fix(tabs): review-driven hardening for the tab-layout foundation and vertical rail

Post-merge follow-ups from the deep review of #334 and #335, so they ship in
the same release as the features.

Tab-layout foundation (#335):
- PUT /api/session-order drops unknown/foreign ids again instead of 400ing
  the whole write, in both the owner and the admin path (single-user requests
  are the synthetic admin, so that path is the one the browser hits). The
  frontend debounces its reorder push and swallows errors, so a session
  deleted inside the debounce window silently cost the user the entire
  reorder - and the endpoint sits on the stable /api/v1 surface, where the
  pre-layout server merged leniently.
- A failed mux restore no longer locks explicit deletions into 500s for the
  process lifetime: runSessionDeletion and webviewDeleted degrade to
  best-effort without layout coordination, while the automated stale sweep
  (runStaleSessionCleanup) stays fail-closed.
- sse-events doc comment: no 'suppressed' hook event exists; hooks stay 8.
- registerSessionWithLayout resolves its owner through ownerLayoutKey()
  instead of a hardcoded '@single'.

Vertical rail (#334) - all rail-awareness gaps in sidebar-only predicates,
unified behind the new _isVerticalTabList() (sidebar OR rail):
- Drag-reorder read the insertion side from clientX in the rail, so
  before/after was effectively arbitrary on vertical rows; the drag-over
  indicators now draw as top/bottom edges there like the sidebar's.
- The active tab is scrolled into view in the rail (Alt+N/palette selection
  used to leave the row below the fold).
- Floating subagent/ultracode windows anchor to the RIGHT of rail tabs, and
  the connector redraw gates (render tail + strip scroll) cover the rail.
- Server-seeded tabOrientation is applied when the async settings load
  resolves, not only at boot, so a fresh device shows the rail immediately.
- The pre-paint script stamps data-tab-orientation and --tab-rail-width
  (sidebar-wins and solo carve-outs included), removing the flash of the
  header strip on every vertical-mode load.
- The session name font defaults to 12px, the sidebar's historical 0.75rem
  size, so installs that never touch the new slider are not restyled.

Also documents the rail in CLAUDE.md (second #sessionTabs host, mover
ordering, the axis-predicate rule) and gives tab-rail-resize.js its
@dependency/@loadorder header. Full gate green (6093 tests); the excluded
browser suite was run by hand - only the known environmental failures
(opencode/codex binaries) remain, identical to pristine master.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CLAUDE.md

@@ -264,13 +264,13 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 
 ### Frontend
 
-Frontend JS modules have `@fileoverview` with `@dependency`/`@loadorder` tags. Load order: `constants.js`(1) → `i18n.js`(1.5) → `mobile-handlers.js`(2) → `voice-input.js`(3) → `notification-manager.js`(4) → `keyboard-accessory.js`(5) → `input-cjk.js`(5.5) → `sanitize-html.js`(5.6) → `app.js`(6) → `terminal-ui.js`(7) → `respawn-ui.js`(8) → `ralph-panel.js`(9) → `orchestrator-panel.js`(9.5) → `cron-ui.js`(9.7) → `settings-ui.js`(10) → `panels-ui.js`(11) → `readmymind-ui.js`(11.3) → `ultracode-panel.js`(11.5) → `approvals-ui.js`(11.6) → `admin-ui.js`(11.7) → `session-ui.js`(12) → `webview-tabs.js`(12.5) → `mobile-overview.js`(12.55) → `home-sessions.js`(12.56) → `entrance-animations.js`(12.6) → `ralph-wizard.js`(13) → `api-client.js`(14) → `subagent-windows.js`(15) → `ultracode-windows.js`(15.5) → `session-lineage.js`(15.6) → `image-input.js`(16). `i18n.js` translates static + newly inserted application DOM while skipping terminal/response/file/user-name surfaces; `input-cjk.js` handles CJK IME composition via an always-visible textarea below the terminal (`window.cjkActive` blocks xterm's onData).
+Frontend JS modules have `@fileoverview` with `@dependency`/`@loadorder` tags. Load order: `constants.js`(1) → `i18n.js`(1.5) → `mobile-handlers.js`(2) → `voice-input.js`(3) → `notification-manager.js`(4) → `keyboard-accessory.js`(5) → `input-cjk.js`(5.5) → `sanitize-html.js`(5.6) → `app.js`(6) → `tab-rail-resize.js`(6.5) → `terminal-ui.js`(7) → `respawn-ui.js`(8) → `ralph-panel.js`(9) → `orchestrator-panel.js`(9.5) → `cron-ui.js`(9.7) → `settings-ui.js`(10) → `panels-ui.js`(11) → `readmymind-ui.js`(11.3) → `ultracode-panel.js`(11.5) → `approvals-ui.js`(11.6) → `admin-ui.js`(11.7) → `session-ui.js`(12) → `webview-tabs.js`(12.5) → `mobile-overview.js`(12.55) → `home-sessions.js`(12.56) → `entrance-animations.js`(12.6) → `ralph-wizard.js`(13) → `api-client.js`(14) → `subagent-windows.js`(15) → `ultracode-windows.js`(15.5) → `session-lineage.js`(15.6) → `image-input.js`(16). `i18n.js` translates static + newly inserted application DOM while skipping terminal/response/file/user-name surfaces; `input-cjk.js` handles CJK IME composition via an always-visible textarea below the terminal (`window.cjkActive` blocks xterm's onData).
 
 **Entrance animations** (`entrance-animations.js`, all OFF by default): opt-in animations for the four things that appear when work starts, chosen per surface via `data-tab-anim` / `data-term-anim` / `data-win-anim` / `data-line-anim` on `<html>`. Defaults are the `legacy` theme, so an untouched install behaves exactly as before and every hook short-circuits on its first line. ⚠️ Tabs and connection lines are **destroyed mid-animation** on every re-render (`_fullRenderSessionTabs()` replaces the strip's innerHTML; `_updateConnectionLinesImmediate()` does `svg.innerHTML = ''`), so both are tracked by id and re-applied to the fresh element with a **negative `animation-delay`** to resume rather than restart. ⚠️ The terminal-pane styles may animate **transform / opacity / clip-path only**, xterm's FitAddon derives rows+cols from `getComputedStyle(parent).width/height`, so animating width/height/padding there would resize the PTY. ⚠️ Window styles other than `beam` transform the window, which moves the rect its connection line is aimed at; `beam` deliberately animates opacity/filter only so its line can draw toward a stable target. Persisted to its own `codeman:*Anim` localStorage keys (per-device, deliberately NOT in the `.strict()` `SettingsUpdateSchema`); picker in App Settings → Appearance, full per-surface lab at `?animlab=1`.
 
 **Mobile tab strip scrolling** (issue #257): under 768px the tab strip is a horizontal scroller (desktop wraps to a second row instead), so the active tab can sit off-screen. Three rules keep it reachable and they only work together: `_updateActiveTabImmediate()` scrolls the selected tab into view via `computeTabScrollLeft()` (pure, in constants.js) using **rect math on the strip's own `scrollLeft`**, never `scrollIntoView()`, which would also scroll the document under a fixed header; `_fullRenderSessionTabs()` **restores `scrollLeft`** across the `innerHTML` rebuild, since ambient rebuilds (a task badge appearing, a session created elsewhere) otherwise snap a mid-swipe strip back to 0; and it re-reveals the active tab **only when it changed** (`_lastRenderedActiveTabId`), so browsing the far end of the strip is not undone by background renders. ⚠️ **The ACTIVE tab is the only one with action icons, and on a phone they can eat it**: `.session-tab.active .tab-name` reserves `min-width: 44px` in the ≤430px block, because a short session name rendered a 13px label against a 50px gear+close cluster, putting the tab's geometric CENTRE on the gear, so a thumb aiming at the tab opened Session Options instead of switching (measured at 360/393/430px; only long names cleared it). ⚠️ **The floor is set by the 10th tab onward, not by the tabs you can see**: `.tab-number` renders only for `_tabIdx < 9`, so tab 10 loses 16px + a gap off its left and its centre sits 10px further right. The centre clears the icons when `reserved > icons + rightEdge - leftRunUp - gap` (= 50 + 9 - 17 - 4 = **38px**), hit-testing snaps to whole pixels so 39px still lands on the gear, and the practical floor is 40px — a NUMBERED tab clears it at 20px, which is exactly why reasoning from the tabs on screen would put the centre back on the gear. `test/mobile-tab-tap-zones.test.ts` recomputes that inequality from the stylesheet, so widening the gear or the padding fails there rather than on a phone. The guarantee is centre-off-the-ICONS, not centre-inside-the-label (on a numberless tab it lands in the gap between them, which still switches). Non-active tabs keep their icons hidden and stay tappable end to end. ⚠️ Mobile no longer hoists the active session to the front of the strip: that reordering ran on full renders only, so tab order flipped depending on which render path fired, and it renumbered the Alt+N badges. Scroll-into-view replaces it; do not reintroduce it.
 
-**Session list layout: header strip or left sidebar** (`sessionListLayout`, App Settings → Appearance → Tabs, default `header`; per-device policy — it IS in `SettingsUpdateSchema` and persists server-side, but `displayKeys` makes a device keep its own value): with many sessions the horizontal strip stops being scannable, so the list can move into a vertical `<aside>` with a filter box and a live count, collapsible to a 44px rail (`--sidebar-width` 260 / `--sidebar-width-collapsed` 44) via **Alt+B** (`toggleSessionSidebar`; Alt, not Ctrl+B, which must reach tmux/readline in the terminal). ⚠️ **There is ONE `#sessionTabs` element and it is MOVED between two hosts** (`#sessionTabsHost` in the header, `#sessionSidebarList` in the aside), never a second list — so every render path, drag-reorder handler and Alt+N index keeps working unchanged, and `applySessionListLayout()` is the only thing that reparents it. ⚠️ It sets `data-session-list` / `data-sidebar` on `<html>` and must run BEFORE `applyTabWrapSettings()`, which is the one owner of `tabs-two-rows`/`tabs-show-folder` and reads those attributes. ⚠️ Leaving sidebar mode **clears `_sidebarFilter`**: the filter box only exists in the aside, so a stale filter would hide sessions from the header strip with no reachable control to clear it. ⚠️ On handhelds the aside is an off-canvas overlay rather than a docked rail, and a closed drawer keeps `display: flex`, so it is marked `inert` + `aria-hidden` (`_isSessionSidebarOverlay()`) or its filter box and ~4 tab stops per session stay in the tab order; the DOCKED desktop rail must never be inerted, its rows are still clickable. The desktop home rail (`home-sessions.js`) defers to it, since both dock the session list flush left.
+**Session list layout: header strip or left sidebar** (`sessionListLayout`, App Settings → Appearance → Tabs, default `header`; per-device policy — it IS in `SettingsUpdateSchema` and persists server-side, but `displayKeys` makes a device keep its own value): with many sessions the horizontal strip stops being scannable, so the list can move into a vertical `<aside>` with a filter box and a live count, collapsible to a 44px rail (`--sidebar-width` 260 / `--sidebar-width-collapsed` 44) via **Alt+B** (`toggleSessionSidebar`; Alt, not Ctrl+B, which must reach tmux/readline in the terminal). ⚠️ **There is ONE `#sessionTabs` element and it is MOVED between hosts** (`#sessionTabsHost` in the header, `#sessionSidebarList` in the aside, `#tabRail` for the vertical rail below), never a second list — so every render path, drag-reorder handler and Alt+N index keeps working unchanged. Exactly TWO functions reparent it and they must run in this order: `applySessionListLayout()` first (sidebar wins), then `applyTabOrientation()` (settings-ui.js), which moves the tabs into `#tabRail` only when the sidebar does not own them. ⚠️ It sets `data-session-list` / `data-sidebar` on `<html>` and must run BEFORE `applyTabWrapSettings()`, which is the one owner of `tabs-two-rows`/`tabs-show-folder` and reads those attributes. ⚠️ **The vertical tab rail** (`tabOrientation`/`tabRailWidth`/`sessionSidebarFontSize`, all per-device display keys that ARE in the schema, like `sessionListLayout`) is a SECOND vertical list next to the sidebar: the orientation setting is silently ignored while the sidebar layout is chosen, desktop/tablet only (`resolveTabOrientation` forces horizontal on mobile), resizable via `tab-rail-resize.js` (which owns terminal refits during the drag). ⚠️ **Axis decisions must use `_isVerticalTabList()`** (sidebar OR rail), never `isSessionSidebarActive()` alone: the rail leaves `data-session-list` at `header`, and the sidebar-only predicate shipped four rail bugs at once (drag insertion side read from clientX, active tab never scrolled into view, floating windows anchored below tabs instead of beside them, connector redraws skipped on rail scroll). The pre-paint script stamps `data-tab-orientation` (+ `--tab-rail-width`) like it stamps the sidebar keys, or vertical mode flashes through the header strip; the name font size defaults to 12px, the sidebar's historical size, so untouched installs are never restyled. ⚠️ Leaving sidebar mode **clears `_sidebarFilter`**: the filter box only exists in the aside, so a stale filter would hide sessions from the header strip with no reachable control to clear it. ⚠️ On handhelds the aside is an off-canvas overlay rather than a docked rail, and a closed drawer keeps `display: flex`, so it is marked `inert` + `aria-hidden` (`_isSessionSidebarOverlay()`) or its filter box and ~4 tab stops per session stay in the tab order; the DOCKED desktop rail must never be inerted, its rows are still clickable. The desktop home rail (`home-sessions.js`) defers to it, since both dock the session list flush left.
 
 **Phone overview home screen** (`mobile-overview.js`, phones only, per-device `mobileOverviewEnabled`, default ON): under 430px the "C" logo shows a session overview (NEEDS YOU / CURRENT SESSIONS / PAST SESSIONS) instead of the welcome overlay; tablet and desktop are unchanged. The branch lives in `showWelcome()`/`hideWelcome()` (terminal-ui.js) behind `shouldUseMobileOverview()`, which is **width-driven** (`getDeviceType() === 'mobile'`) because this is a layout decision, unlike the settings namespace which stays handheld-based. ⚠️ The container ships with the `hidden` attribute and only this module removes it: never give `.mobile-overview` a bare `display` rule, since desktop does not load `mobile.css` (`media="(max-width: 1023px)"`) and would then render it unstyled. Live re-renders ride on the tail of `_renderSessionTabsImmediate()` (every state change it needs already funnels there); PAST rows come from one `_fetchUnifiedSessions(60)` per home-screen visit and resume through the shared `resumeHistorySession()`, so they behave exactly like the welcome screen's Resume list. ⚠️ Two things must stay in lockstep with surfaces outside this module, because divergence reads as a bug rather than a style: the split Run button carries the **toolbar's own classes** (`btn-toolbar btn-run mode-<backend>` / `btn-run-gear`) so the per-backend gradient and the light-skin overrides apply unchanged (mobile.css must therefore set no `background`/`color` on it), and row status uses the **session-tab language** (green dot when fine, `pulse` while working, yellow blinking row when waiting for input, red blinking row when a question is pending, mirroring `tab-alert-idle`/`tab-alert-action`). The picker mirrors the toolbar run-mode menu (`setRunMode()` + `run()`, `openWebviewFromMenu()` for saved dashboards) and deliberately omits its Recent-Sessions block, since PAST SESSIONS is that. Status pills carry `data-i18n-skip` (generic words like "idle" collide with state strings elsewhere).