docs(split-pane): short CLAUDE.md rule, stale module count, wiki entries, shortcut-handler caveat

CLAUDE.md previously only mentioned split-pane in the load-order list,
with nothing in the Architecture/frontend prose the way every other
feature gets, and its own module count was one stale (34, should have
been bumped to 35 when terminal-split.js was added). Add a short
pointer-style paragraph next to the other terminal features, fix the
count.

docs/wiki/The-Dashboard.md's header button table and
docs/wiki/Settings-Reference.md's header chips list are the two
user-facing surfaces that never mention Split at all; added both, plus
a note that the feature is desktop-only regardless of the setting.

docs/split-pane-sessions-plan.md: recorded the one design note that
isn't a code change — the global capture-phase shortcut handler always
resolves against Pane A, so Ctrl+L/Ctrl+W typed into Pane B affects the
other session. Not fixed for v1, same reasoning as the rest of the
"deliberately plainer" section.

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

CLAUDE.md

@@ -171,7 +171,7 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 | **Attachments**  | `src/attachment-registry.ts`, `attachment-magic`, `generated-artifact-attachments`, `session-attachment-history`, `document-preview-cache`, `document-thumbnailer`, `document-conversion-limiter`, `config/attachment-guard` | See Key Patterns                                                                                 |
 | **Plan**         | `src/plan-orchestrator.ts`, `src/prompts/*.ts`, `src/templates/` (`claude-md.ts` + `case-template.md`) | `templates/` holds the CLAUDE.md scaffold generated into new cases                                |
 | **Web**          | `src/web/server.ts` ★, `sse-events.ts`, `routes/*.ts` (27 modules + barrel; `session-routes.ts` ★), `route-helpers.ts`, `ports/*.ts`, `middleware/auth.ts`, `schemas.ts`, `self-update.ts`, `plan-usage-latest.ts`, `ws-connection-registry.ts`, `heic-jpeg-converter.ts` + `heic-jpeg-worker.ts` |                                                                                                  |
-| **Frontend**     | `src/web/public/app.js` (~6.9K lines, core) + 34 modules + `sw.js` (+ `voice-pcm-worklet.js`, fetched from JS, not in the load order) | See Frontend section for the load order, which is authoritative                                  |
+| **Frontend**     | `src/web/public/app.js` (~6.9K lines, core) + 35 modules + `sw.js` (+ `voice-pcm-worklet.js`, fetched from JS, not in the load order) | See Frontend section for the load order, which is authoritative                                  |
 | **Types**        | `src/types/index.ts` (barrel) → 22 domain files; also `src/types.ts` root re-export                    | See `@fileoverview` in index.ts                                                                  |
 
 ★ = Large, central file (>50KB) — read its `@fileoverview` first. All files have `@fileoverview` JSDoc — read that before diving in. Discovery aid: `grep -l '@fileoverview' src/web/routes/*.ts` lists all route modules; same grep works for `src/types/`, `src/web/public/*.js`.
@@ -261,6 +261,8 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 
 **Full-scrollback replay**: `GET /api/sessions/:id/terminal?full=1` returns the entire tmux scrollback, bounded by the configured history limit. On success the capture is returned ALONE (`source='mux-full-history'`), superseding the byte buffer so nothing duplicates. The first load of each non-shell TUI session per page requests `full=1` (`_fullHistoryLoaded` Set); Shell selection and automatic drop recovery always use a bounded 1 MiB `?tail=` window. Shell loads the rest only when **Load full history** is pressed; ordinary scrolling must not trigger a multi-megabyte reset+replay on xterm's main thread. Other modes may re-pull at the TOP (cooldown-guarded — tmux repaints bursty output in place, so browser scrollback shrinks while tmux's history stays complete). Live writes are one-chunk-in-flight, released by xterm's parse callback, so xterm's private queue cannot bypass the browser's 128 KiB render cap. While WebSocket owns terminal I/O, duplicate SSE terminal events are dropped before JSON parsing, and recovery is single-flight per active session. ⚠️ **A `full=1` capture ENDS with a cursor move back to the pane's own caret position**, counted UP from the last replayed row — without it the caret stays where the last character landed, which for an agent CLI is the status line, and every cursor-relative update the CLI sends afterwards is measured from the wrong row. The move is relative, not `CUP`: absolute row addressing is only right while the browser's rows equal the pane's, and `resizeWindow` does not wait for tmux, so a capture can be taken before a requested resize applies. That makes row alignment load-bearing on this path: no transform that can DELETE A LINE may run over the capture, so it keeps its trailing blank rows and skips redraw-bloat stripping, the banner trim and the leading-whitespace strip. ⚠️ Those three skips key on whether a capture actually CAME BACK (`isFullCapture`), never on `?full=1` alone — the fallback to the byte history is a stream of successive frames that must still be stripped, and a session with no mux takes it on every load. A capture holding nothing visible returns '' so the byte history survives instead of a blank screen replacing it. ⚠️ A full re-pull must never DOWNGRADE the buffer: a repaint-mode CLI pane keeps no tmux history, so its capture is one frame and the reset+rewrite would delete history mid-scroll — `_replayWouldShrinkBuffer()` refuses it and slows that session's cooldown to 60s. ⚠️ **A visible capture now REPORTS the geometry it was taken at** (`captureCols`/`captureRows`, #435), because a frame built for a pane taller or wider than the browser is damaged two ways at once (overflow rows clamp onto the last line; a narrower browser wraps every painted row) and nothing in the response used to say so. Both fields are ABSENT when no frame was positioned, so every consumer tests `Number.isFinite`, never truthiness: a `display-message` cursor query that fails makes `capturePaneBuffer` return the raw capture while the route still labels it `mux-visible`. The comparison runs on `mux-visible` ONLY, the replay is capped at one attempt, and a pane that cannot be sized to fit latches in `_geometryRetryUseless` so it is diagnosed once per session rather than on every tab switch. → [architecture-invariants#full-scrollback-replay](docs/architecture-invariants.md#full-scrollback-replay)
 
+**Split-pane sessions** (`showSplitButton`, header button, default OFF, desktop-only, per-device): a second live session ("Pane B") beside the active one, in its own `SplitTerminalPane` (terminal-split.js) with its own xterm + WebSocket, resizable via a draggable divider. Deliberately plainer than the primary pane — no local-echo overlay, CJK IME, or touch handlers — and NOT persisted across reloads. → [architecture-invariants#split-pane-sessions](docs/architecture-invariants.md#split-pane-sessions)
+
 **Terminal touch gestures: link taps and text selection**: on a touch device xterm's own handlers see neither — `touch-action: none` plus touchstart's preventDefault suppress the browser's compatibility mouse events, `_installMobileTapMouseGuard` drops the trusted ones that still arrive, and the synthetic `mousedown`/`mouseup` pair dispatched for mouse REPORTING goes to the `.xterm` root, an ANCESTOR of the screen element the linkifier and SelectionService listen on. So both gestures are driven explicitly. ⚠️ **A tap activates the link under it** through the SAME provider that feeds the hover linkifier (`_terminalLinkAtPoint`, containment mirroring xterm's `_linkAtPosition`), synchronously inside `touchend` — that is what keeps the user gesture `window.open` needs — and BEFORE any mouse report, mirroring `_handleDesktopTerminalClick`'s skip for a hovered link. Two rows keep their meaning: the caret's logical line (`_tapIsOnCaretLine`, where a tap places the cursor in text the USER typed) and TUI-owned rows (`_isActionableMobileTerminalTap`, answering a dialog). ⚠️ The caret line is the boundary rather than the tap INTENT, because a shell classifies every tap as `'input'` and gating on that would leave every URL in shell output inert. ⚠️ **Long-press selects** by driving xterm's public `select()` (renderer-independent — under WebGL the glyphs are pixels and native selection cannot exist), drag or a further tap extends, and Copy goes through `copyTerminalSelection()` for its execCommand fallback on plain-HTTP installs. Three guards are load-bearing and each came from a real phone: the compat mouse pair after `touchend` (xterm focuses on mousedown and SelectionService resets the model there, so the keyboard sprang up and the selection vanished on lift), the platform's own ~500ms long-press (Android Chrome focuses the nearest editable element — the helper textarea — through no event a handler can preventDefault, so a bounded focus guard blurs it and `contextmenu` is suppressed for the gesture window), and `copyTerminalSelection()`'s closing `terminal.focus()` (right on desktop, wrong on a phone). Tests: `test/terminal-touch-tap.test.ts`.
 
 **Auto Copy (copy-on-select)** (`autoCopySelection`, per-device, default OFF): a finished terminal selection lands on the clipboard with no keystroke. ⚠️ It fires at the END of a gesture, never in `onSelectionChange` (that callback runs per cell crossed, so copying there is one clipboard write per mouse move); it only ARMS `_autoCopyPending`, and a document-level `mouseup` listener flushes. ⚠️ The flush is SYNCHRONOUS inside the handler because both clipboard paths need user activation (Firefox gates `navigator.clipboard.writeText` on it, and the plain-HTTP `execCommand` fallback must run in the gesture's own task); a timer or a wait for `onSelectionChange` loses it, invisibly in Chrome. ⚠️ Touch needs its OWN calls from `_endTouchSelectionGesture()`/`_selectTouchSelectionLine()`: that path `preventDefault()`s its touchend, so no mouseup ever arrives and the toggle would be dead on phones. ⚠️ Unlike `copyTerminalSelection()` it must NOT clear the selection (the text would vanish under the cursor that highlighted it) and must NOT focus the terminal (that opens the on-screen keyboard over it); focus is RESTORED to whatever held it, which only matters for the `execCommand` fallback. Guards are pure in `decideAutoCopy()` (constants.js): off, blank/whitespace-only, and a 1M-char cap (an autoscrolling drag can sweep the whole 50k-line scrollback), refused rather than truncated with a toast pointing at Ctrl+C. Silent on success except once per page load; failures toast, throttled 10s. Tests: `test/terminal-auto-copy.test.ts`.

docs/split-pane-sessions-plan.md

@@ -90,6 +90,13 @@ If this asymmetry actually bothers you in daily use, promoting Pane B to full
 parity is a scoped v2 (extract the shared logic already once you have two
 call sites to compare, rather than guessing the right abstraction now).
 
+One more asymmetry worth naming here rather than discovering by surprise:
+while both panes accept keyboard input, the global capture-phase shortcut
+handler (`app.js`) always resolves against Pane A — it has no notion of
+which pane currently has focus. So Ctrl+L or Ctrl+W typed while Pane B has
+focus clears or closes Pane A, not the session you were actually typing
+into. Not fixed for v1, same reasoning as the rest of this section.
+
 ## Components
 
 ### 1. `SplitTerminalPane` (new, `terminal-split.js`)

docs/wiki/Settings-Reference.md

@@ -55,12 +55,14 @@ supervised by systemd or launchd; npm installs report as non-updatable. See
 Chips for every optional header control, with a live preview of the resulting header:
 
 Run, Font Size, System Stats, Redraw Terminal, Response Viewer, Away Digest, Session
-Manager, Attachments, File Viewer, Multi-monitor, Plan Usage, Lifecycle Log, Monitor,
+Manager, Attachments, File Viewer, Multi-monitor, Split, Plan Usage, Lifecycle Log, Monitor,
 Project Insights, File Browser, Subagents, Approvals Inbox, Read My Mind, Ultracode Agents,
 Ultracode Windows, Cron.
 
 Most default to off. The stock desktop header is system stats, File Viewer, and the gear.
-New header controls never appear on phones.
+New header controls never appear on phones. Split is desktop-only regardless of this
+setting — the button and the feature both stay off below a ~1180px viewport, where two
+resizable panes plus their divider have nowhere to go.
 
 This section also holds background-agent tracking, including whether to track agents for
 every session or only the active tab.

docs/wiki/The-Dashboard.md

@@ -116,6 +116,7 @@ The right side of the header. Almost all of these are off until you enable them
 | Lifecycle Log          | Off                | Session start, exit, and kill audit trail.                                       |
 | Cron ⏰                | Off                | Scheduled jobs.                                                                   |
 | Multi-monitor          | Off, macOS         | Opens a window spanning every display.                                            |
+| Split                  | Off, desktop only  | View a second session beside the active one, with a draggable divider.           |
 | Tunnel indicator       | When a tunnel runs | Cloudflare tunnel status.                                                        |
 | Admin panel            | Multi-user only    | User administration.                                                              |