fix(terminal): clean a copy once, and reach every pane that copies

Review fixes for #469.

The Ctrl+C branch cleaned the selection to decide whether to copy and then
passed that cleaned string to copyTerminalSelection(), which cleans again. The
trailing trim is a fixed point, so that was safe until this PR; the margin
strip is not, because it takes the lesser of the declared width and the run
every line shares, so a second pass takes up to `margin` columns more. The
branch now gates on the cleaned string and hands the raw one on. Verified in
chromium with a real drag, a real Ctrl+C and a real clipboard read on a live
claude pane: an on-screen `      fix(terminal): trim it` reaches the clipboard
as `    fix(terminal): trim it`, and reverting the branch reproduces the
reported `  fix(terminal): trim it`.

Pane B of a split resolves its own width. `_cliGutterColumns()` and
`_normalisedSelectionRange()` take the session and the terminal to read,
defaulting to the primary pane's, so Pane B looks its own run mode up instead
of keeping a margin Pane A drops on the same keystroke. Verified live with two
claude panes open side by side.

A detached session window (`/session/:id`) receives the gutter map. The
injection sat inside the block that skips the run menu's payloads for a solo
window, so the toggle worked in the main window and did nothing in the popup on
the same device. It needs no availability probe, so it moved below that block
and the solo window still carries none of the payloads it skipped before.

The settings description said the width is measured and named Codex as exempt.
Nothing is measured, and Codex is one of the two panes that are stripped.
docs/wiki/Settings-Reference.md gains the row every Terminal and Input toggle
carries. CLAUDE.md no longer says the clean touches trailing runs "and nothing
else" one sentence before the leading-margin rule, and both it and
docs/architecture-invariants.md record that the strip is not idempotent.

Two round-trip tests run on a mode that declares a gutter, which the existing
copyTerminalSelection cases could not, since they all use the harness default
mode that declares none. The Ctrl+C branch itself is pinned at the source,
because it lives inside initTerminal's attachCustomKeyEventHandler closure over
a real xterm the vm harness cannot build. Both pins fail on the reintroduced
bug. Gate: 7865 passed, 0 failed.

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

docs/architecture-invariants.md

@@ -310,7 +310,7 @@ Copy goes through `_copyText()` (Clipboard API, then hidden-textarea + `execComm
 
 **The main terminal's four copy paths clean the selection first** (`CodemanCopySelection.clean` in constants.js, pure; `cleanedTerminalSelection()` in terminal-ui.js is the half that reads the live terminal). Those four are the `Ctrl+C` chord, right-click, the phone selection button and Auto Copy. ⚠️ Three routes still copy the RAW padded rows, all of them predating the clean: the browser's own Edit → Copy, which xterm's own `copy` listener on the terminal element serves with `selectionText` directly; a `copy-selection` shortcut the user disabled in App Settings, where nothing calls `preventDefault()` and that native listener runs; and the subagent/teammate windows, which build their own `Terminal` in panels-ui.js with no copy wiring at all. xterm hands back whole screen ROWS and its own trim drops only cells that were never written to, so the real spaces a full-screen TUI paints across the unused part of a row count as content and reach the clipboard. Measured against Claude Code in a 282-column pane, single lines arrived carrying 138 trailing spaces on top of the two-space transcript indent. The clean drops each line's trailing run, and strips a LEADING margin when the pane behind the selection turns out to have one. Four rules keep it honest:
 
-1. **A leading strip uses the width the CLI DECLARES, never one derived from the pane.** `capabilities.transcriptGutter` (CLI registry, a bounded integer) is the whole source: claude and codex each declare 2, no other stock entry declares any, and an entry that declares nothing never has a margin taken off a copy. The server publishes the map as `window.__codemanTranscriptGutter`, built by filtering `enabledClis()` on that capability rather than by listing ids, and `_activeCliGutterColumns()` (terminal-ui.js) looks the active session's mode up in it. ⚠️ **Three ways of deriving the width from the text were built and measured, and two of them shipped looking correct.** The selection's own shared indent fired on **73%** of 401,445 three-row windows across 1,010 tracked files, because a three-row window of nested YAML shares an indent for the same reason a margin does. **Painted trailing padding** — a full-screen TUI writes real spaces across the part of a row it is not using, while a shell leaves those cells never-written for xterm to trim — has no false positives and never over-stripped, and is nonetheless a function of pane WIDTH: the padding exists only while a rendered line stops short of the CLI's own layout width, and Claude Code's prose wraps to fill it. Dragging the same two prose rows of one live transcript at five window sizes, the share of rows carrying padding measured 44%, 6%, 6%, 7% and 87% at 123, 160, 198, 235 and 298 columns, so at every ordinary size the strip did nothing at all while every test and every 282-column measurement said it worked. The **narrowest indent on the surrounding rows** fires at every width and over-strips about 1% of selections, because a file listing inside the transcript can be the narrowest thing on screen. ⚠️ The declared width is a **CEILING, not the answer**: `clean()` strips the lesser of it and the run every selected line shares, so a block can only ever shift as a unit, the relative structure inside a selection survives by construction, and a selection reaching column 0 loses nothing. That is what keeps a `git log` body at its own four spaces inside an agent's two-column gutter. Measured over 1,392,281 selections — every 1, 2, 3, 5, 10 and 20-row window of real Claude screens replayed from live PTY streams at 100, 120, 160, 198, 235 and 282 columns — it over-strips none, breaks no relative indent and alters no text, at 100% of the selections whose own indent covers the gutter. ⚠️ Nothing reads the terminal buffer on this path; the old version scanned up to ~240 rows per `Ctrl+C` to measure a width the CLI can simply state.
+1. **A leading strip uses the width the CLI DECLARES, never one derived from the pane.** `capabilities.transcriptGutter` (CLI registry, a bounded integer) is the whole source: claude and codex each declare 2, no other stock entry declares any, and an entry that declares nothing never has a margin taken off a copy. The server publishes the map as `window.__codemanTranscriptGutter`, built by filtering `enabledClis()` on that capability rather than by listing ids, and `_cliGutterColumns()` (terminal-ui.js) looks that session's mode up in it, defaulting to the active session and taking an explicit id for Pane B of a split. ⚠️ **Three ways of deriving the width from the text were built and measured, and two of them shipped looking correct.** The selection's own shared indent fired on **73%** of 401,445 three-row windows across 1,010 tracked files, because a three-row window of nested YAML shares an indent for the same reason a margin does. **Painted trailing padding** — a full-screen TUI writes real spaces across the part of a row it is not using, while a shell leaves those cells never-written for xterm to trim — has no false positives and never over-stripped, and is nonetheless a function of pane WIDTH: the padding exists only while a rendered line stops short of the CLI's own layout width, and Claude Code's prose wraps to fill it. Dragging the same two prose rows of one live transcript at five window sizes, the share of rows carrying padding measured 44%, 6%, 6%, 7% and 87% at 123, 160, 198, 235 and 298 columns, so at every ordinary size the strip did nothing at all while every test and every 282-column measurement said it worked. The **narrowest indent on the surrounding rows** fires at every width and over-strips about 1% of selections, because a file listing inside the transcript can be the narrowest thing on screen. ⚠️ The declared width is a **CEILING, not the answer**: `clean()` strips the lesser of it and the run every selected line shares, so a block can only ever shift as a unit, the relative structure inside a selection survives by construction, and a selection reaching column 0 loses nothing. That is what keeps a `git log` body at its own four spaces inside an agent's two-column gutter. Measured over 1,392,281 selections — every 1, 2, 3, 5, 10 and 20-row window of real Claude screens replayed from live PTY streams at 100, 120, 160, 198, 235 and 282 columns — it over-strips none, breaks no relative indent and alters no text, at 100% of the selections whose own indent covers the gutter. ⚠️ Nothing reads the terminal buffer on this path; the old version scanned up to ~240 rows per `Ctrl+C` to measure a width the CLI can simply state. ⚠️ **The margin strip is not idempotent, so no caller may clean twice.** It takes the lesser of the declared width and the shared run, so a second pass takes up to `margin` columns more off whatever the first left. The trailing trim alone is a fixed point, and `copyTerminalSelection()` relied on that by re-cleaning whatever argument it was handed, which dedented every claude and codex copy twice on the `Ctrl+C` path — the most-used of the four, while right-click, the phone selection button and Auto Copy stayed correct because each hands over the raw selection or reads it live. The gate still tests the CLEANED string, so a padding-only selection still falls through to the PTY, and the RAW string is what travels on. A source-level test pins that branch, because it lives inside `initTerminal`'s `attachCustomKeyEventHandler` closure over a real xterm that the vm harness cannot build.
 2. **A COLUMN selection is returned untouched.** Alt+drag makes one (xterm's `shouldColumnSelect` keys on `altKey` alone, and neither `Terminal` Codeman builds passes the one option, `macOptionClickForcesSelection`, that would disable it), and a rectangle's rows lining up is the whole point of the gesture. xterm exposes the mode nowhere public, so the check reads `terminal._core._selectionService._activeSelectionMode` (`SelectionMode.COLUMN` is 3) and cleans normally if a future xterm renames it.
 3. **The mid-row flag reads an ORDERED range, and it governs one line.** ⚠️ `getSelectionPosition()` is reversal-aware on the pinned xterm and the review note that called it the raw mousedown anchor is out of date: `CoreBrowserTerminal.ts` reads `_selectionService.selectionStart`, whose getter returns `SelectionModel.finalSelectionStart`, and that swaps the pair when `areSelectionValuesReversed()` says so. Driving a real upward mouse drag through chromium against xterm 6.0 reports the same range as the downward drag of the same rows. `_normalisedSelectionRange()` orders the pair anyway, because the private model one layer down exposes unnormalised fields under the same two names, and a reversed pair would put the mid-row flag on the wrong end of the drag. `range.start.x > 0` then means the first selected line began mid-row and never carried the margin, so that line alone is left out of both the shared-indent ceiling and the strip. ⚠️ This is the ONE thing the mousedown column still decides and it decides it for that line only. In the dropped version it decided whether the first row joined the measurement, which changed what **every** row lost, so the same three rows produced three different clipboard results depending on where the click landed.
 4. **The emptiness gate is `trim()`, not truthiness, and it still clears the selection.** A multi-row drag across padding cleans to line breaks alone, which are truthy, and a bare newline pasted into a chat composer submits it. ⚠️ The clear is FEEDBACK, not protection for the interrupt, and the comments that said otherwise were describing the pre-clean code: the `Ctrl+C` gate above now tests the CLEANED selection, so a padding-only selection left set cleans to `''` on every later press and falls through to the PTY as `0x03` anyway. What the clear buys is that a highlight which copied nothing does not linger unexplained, which is also what the toast is for.

docs/wiki/Settings-Reference.md

@@ -46,6 +46,7 @@ supervised by systemd or launchd; npm installs report as non-updatable. See
 | Extended Keyboard Bar         | Per device           | Which accessory bar phones get. Shell sessions override it while they are active. |
 | Wheel Scrolls Local History   | Off                  | Keeps the wheel on the local buffer instead of forwarding it to the CLI. |
 | Auto Copy Selection           | Off                  | Copies highlighted terminal text to the clipboard the moment you finish selecting it. Ctrl+C still copies on demand. |
+| Trim The Pane Margin On Copy  | On                   | Takes the left margin a full-screen agent CLI paints down its own edge off a copy, so the text pastes flush. Each CLI declares its own width, and the strip never exceeds the indent every selected line shares, so nesting is kept. Claude Code and Codex declare a margin; a shell does not. |
 | Normal / Bold font weight     | xterm defaults       | Per device, each slot from 100 to 900. The bundled JetBrains Mono renders every step, so a lighter normal weight makes Claude's bold headings stand out. Applies live to the terminal, both echo overlays and open team panes. |
 | WebGL Renderer                | On                   | With a GPU-stall watchdog that falls back to DOM rendering.            |
 | Gesture Control               | Off                  | Camera hand tracking. Also needs `CODEMAN_GESTURE=1` on the server.    |