feat(home): dock the desktop tab list as a left rail with age stamps

The open-tabs list on the welcome screen was a fixed 256px card floating
vertically centered in the left gutter, which read as debris rather than
chrome and left 12px type stranded on a wide display.

- Dock it: left/top/bottom 0, full height, hairline right border and a soft
  background fade. The centered welcome content still does not move.
- Scale it off one knob: width clamp(250px, 19vw, 430px) plus a fluid
  font-size on .home-sessions, every child sized in em. Measured 250px/12.2px
  at the 1180px gate, 380px/15px at 2000px, 430px/17px at 2938px; the gap to
  the centered content never goes negative.
- Show when each session was first created and last active, on a full-width
  footer line so it does not fight the status pill, exact dates in the title.
  Both stamps refresh in place on a 20s clock (disarmed when the home screen
  goes away) rather than by re-rendering, which would restart every row's
  blink animation and working ring twice a minute.
- Mute idle green: dot and pill mix toward --text-muted, so idle reads as
  greyed-out next to the vivid green of a working session. Mixed rather than
  hardcoded, so every skin keeps its own green.

Verified in a browser at 1180/2000/2938px and on a light skin, plus
test/home-sessions.test.ts, frontend-syntax, public-assets, prettier and a
PostCSS parse of styles.css.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -254,7 +254,7 @@ Frontend JS modules have `@fileoverview` with `@dependency`/`@loadorder` tags. L
 
 **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).
 
-**Desktop home tab column** (`home-sessions.js`, desktop only): the welcome overlay centers ~560px of content in a ~1400px window, so its left gutter is dead space; it now carries the open tabs as a vertical list. Rows are in **tab order**, not sorted by urgency like the phone overview, because the row badges are the Alt+1..9 indices. State classification is REUSED from mobile-overview.js (`_mobileOverviewState`/`_mobileOverviewCaseFor`), which is why the module loads after it. ⚠️ The column is `position: absolute` so the centered content never moves, which is exactly why it needs a **width gate in two places** — `HOME_SESSIONS_MIN_WIDTH` (1180) in the JS plus a `max-width: 1179px` media query as the backstop for a resize that outruns the matchMedia listener; drift between them means a column overlapping the search panel, and `test/home-sessions.test.ts` pins them equal. ⚠️ `.home-sessions` is `display: flex`, so `[hidden]` must be re-asserted as `display: none` or the module's only visibility lever does nothing. Working state is deliberately byte-identical to the phone's: pulsing green dot + the `tab-load-spin` ring reused from the tab strip + the same green halo (added to `.mobile-overview-dot--working` at the same time), so "working" reads the same on every surface. Live re-renders ride the tail of `_renderSessionTabsImmediate()` alongside the phone overview.
+**Desktop home tab rail** (`home-sessions.js`, desktop only): the welcome overlay centers ~560px of content in a ~1400px window, so its left gutter is dead space; it carries the open tabs as a rail **docked flush to the left edge, full height** (a vertically centered card floating mid-gutter read as debris). Rows are in **tab order**, not sorted by urgency like the phone overview, because the row badges are the Alt+1..9 indices, and each carries **created / last-active** stamps. State classification is REUSED from mobile-overview.js (`_mobileOverviewState`/`_mobileOverviewCaseFor`), which is why the module loads after it. ⚠️ The rail is `position: absolute` so the centered content never moves, which is exactly why it needs a **width gate in two places** — `HOME_SESSIONS_MIN_WIDTH` (1180) in the JS plus a `max-width: 1179px` media query as the backstop for a resize that outruns the matchMedia listener; drift between them means a rail overlapping the search panel, and `test/home-sessions.test.ts` pins them equal. ⚠️ `.home-sessions` is `display: flex`, so `[hidden]` must be re-asserted as `display: none` or the module's only visibility lever does nothing. ⚠️ Size scales with the viewport off **one knob**: `width: clamp(250px, 19vw, 430px)` plus a fluid `font-size` on `.home-sessions`, with every child sized in `em` — reintroducing `rem`/px type inside the block silently breaks the scaling, and widening the clamp past the gutter reintroduces the overlap the gate exists to prevent. The age stamps are refreshed **in place** by a 20s clock (`_tickHomeSessionsTimes()`, disarmed in `hideHomeSessions()`), never by re-rendering, which would restart every row's blink and working ring. Working state is deliberately byte-identical to the phone's: pulsing green dot + the `tab-load-spin` ring reused from the tab strip + the same green halo (added to `.mobile-overview-dot--working` at the same time), so "working" reads the same on every surface; **idle** is deliberately NOT that green — dot and pill mix toward `--text-muted` so a glance separates running from sitting. Live re-renders ride the tail of `_renderSessionTabsImmediate()` alongside the phone overview.
 
 **Command palette + shortcut registry**: `Ctrl/Cmd/Alt+K` opens the session palette; shortcuts live in a rebindable registry (`DEFAULT_SHORTCUTS`/`getShortcutRegistry()`/`matchesShortcutEvent()` in app.js, overrides in `settings.shortcutOverrides`). ⚠️ Palette-chord keys must ALSO be swallowed in `attachCustomKeyEventHandler` (terminal-ui.js) or xterm writes the control byte (0x0B) into the PTY. ⚠️ `saveAppSettings()` rebuilds settings from the DOM, so keys edited elsewhere (`shortcutOverrides`, `showTokenCount`, `showCost`) need explicit `_prev` carry-over. ⚠️ **Smart copy (`Ctrl+C`)** lives in that same handler: with a selection it copies, with none it must `return true` **without** `preventDefault()` or the interrupt is lost. `copyTerminalSelection` is deliberately absent from `SHORTCUT_ACTIONS` because the generic capture loop preventDefaults every match it dispatches. → [architecture-invariants#command-palette-and-shortcut-registry](docs/architecture-invariants.md#command-palette-and-shortcut-registry)