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`.