fix(terminal): ship the copy clean as a trailing trim, without the shared dedent

#451 cleaned two things on copy. The trailing trim is right and every native
terminal does it. The shared leading-indent strip is this project's own rule,
and it is dropped here rather than shipped.

Measured against the shipped transform over 401,445 three-row windows across
1,010 tracked files in this repo, it fired on 73% of them: 92% inside a YAML
workflow, 76% over `git log` output, 48% in a TypeScript source. No width
threshold separates a margin from content because they are the same widths, a
live Claude Code pane's own margins measuring 2 and 5 columns while the most
common non-TUI shared run is 4. The failure modes are not symmetric either: a
wrong trailing trim costs nothing, while a wrong dedent silently deletes
information that was on the screen, with nothing in the clipboard to hint at
it, on git log bodies, on indented code read out of cat (semantic in Python),
on git diff context rows where the leading space is the marker, and on stack
traces.

It also could not be made self-consistent cheaply. Whether the first row joined
the measurement depended on the mousedown COLUMN, which the user never sees, so
one block of three rows produced three different clipboard results; and the
flag read getSelectionPosition().start, which is xterm's mousedown anchor and
is never normalised, so dragging UP through a block read it off the bottom row.
The PR's test stub hardcoded a downward drag, so its suite could not express
that case.

The transform, the wiring, the tests, the invariants, CLAUDE.md, the wiki page
and the changeset all move together. The test block now pins the ABSENCE as a
contract, with the git log, Python and git diff cases as its examples, so this
is not re-derived later. If it is ever revisited, the one qualification that
measured clean is painted trailing padding: zero false positives over all
401,445 windows.

Also from the review: the comments and invariant rule justifying the
padding-only clear described the pre-change code (the Ctrl+C gate reads the
CLEANED selection now, so such a selection falls through to the PTY on its own
and the clear is feedback rather than protection), the new 'Nothing to copy'
toast gained its zh-CN entry, and the invariants paragraph no longer repeats
its own opening sentence.

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

docs/architecture-invariants.md

@@ -306,13 +306,13 @@ Invariants:
 
 Copy goes through `_copyText()` (Clipboard API, then hidden-textarea + `execCommand`), not raw `navigator.clipboard`, because `install.sh`'s LAN option serves plain HTTP where `navigator.clipboard` is undefined; the fallback steals focus, so the terminal is refocused afterwards. Related: xterm registers its own `copy` listener on the terminal element gated on `hasSelection()`, which is why right-click → Copy has always worked. Selection itself is unavailable on touch devices by design (`user-select: none` on the terminal subtree), and in `shell`/`opencode`/`antigravity` tabs the TUI owns the mouse, so selecting there needs Shift+drag. Tests: `test/terminal-copy-selection.test.ts` (gate + wiring invariants), `test/terminal-copy-shortcut.test.ts` (browser, real key presses).
 
-**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 removes the leading run only when every selected row shares one, which makes it a no-op for shell output. Three rules keep it honest:
+**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. Two rules keep it honest:
 
-1. **A one-row selection keeps its leading run.** One row shares nothing with anything, so that run is content — stripping it would silently reindent a single line of `git log` body text or one line out of `less`. ⚠️ A drag that STARTED mid-row lowers that bar to one measured row, because the partial first line is counted toward the two-row total and then skipped by the measurement. That is deliberate: both rows of a wrapped paragraph wear the TUI's margin and the drag only hid the first one's, so the second row's margin still goes. The cost is that a two-row mid-row drag over genuinely indented content loses that indent.
+1. **Trailing padding only. A shared LEADING indent is deliberately NOT stripped**, and that is a decision rather than an omission: it was built, measured and dropped before #451 merged. It looks like the mirror image of the trailing trim and is not, because no native terminal does it and the transform cannot tell a TUI's margin from content that is genuinely indented. Measured over 401,445 three-row windows across 1,010 tracked files in this repo it fired on **73%** of them (92% inside a YAML workflow, 76% over `git log` output, 48% in a TypeScript source), and no width threshold separates the two because they are the same widths: a live Claude Code pane's own margins measure 2 and 5 columns while the most common non-TUI shared run is 4, sitting between them. The failure modes are what settle it. A wrong trailing trim costs nothing; a wrong dedent silently deletes information that was on screen, with no signal and nothing in the clipboard to hint at it, and it is wrong on `git log` bodies, on indented code read out of `cat` (semantic in Python), on `git diff` context rows where the leading space is the marker, and on stack traces. ⚠️ It also could not be made self-consistent cheaply: whether the first row joined the measurement depended on the mousedown COLUMN, which the user never sees, so one block of three rows produced three different clipboard results, and the flag read `getSelectionPosition().start`, which is the mousedown anchor xterm never normalises, so dragging UP through a block read it off the bottom row (the PR's test stub hardcoded a downward drag, so its suite could not express the case). If it is ever revisited, the one qualification that measured clean is **painted trailing padding** (a full-screen TUI writes real spaces across every row, while a shell pane leaves those cells never-written for xterm to trim): zero false positives over all 401,445 windows, no new plumbing. It still mangles a `git log` body sitting inside an agent's own gutter, which is why it was not taken.
 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 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. ⚠️ Returning without `clearSelection()` there would leave the raw selection set, and since the `Ctrl+C` gate above tests the RAW selection, every later `Ctrl+C` would copy nothing instead of interrupting — the exact way rule 1 of smart copy gets lost.
+3. **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.
 
-All four paths go through it: the `Ctrl+C` chord, right-click, the phone selection button and Auto Copy. Tests: `test/terminal-copy-clean.test.ts`.
+Tests: `test/terminal-copy-clean.test.ts`.
 
 ### Auto Copy (copy-on-select)
 

docs/wiki/Keyboard-Shortcuts.md

@@ -34,7 +34,7 @@ Press `Ctrl+?` in the app for the same list in a floating overlay.
 | Right-click             | Copy the selection. With nothing selected the native menu is left alone. |
 | `Ctrl+Z`                | Swallowed in agent sessions so a running CLI cannot be suspended. Normal job control in a shell. |
 
-Anything you copy is cleaned on the way to the clipboard. Each line loses the padding spaces a full-screen program paints across the rest of the row, and a selection covering several rows also loses the indent every one of those rows shares, which is usually the program's own margin rather than your text. A one-row selection keeps its indent, and an `Alt+drag` rectangular selection is copied exactly as it looks, so its columns stay lined up.
+Anything you copy is cleaned on the way to the clipboard: each line loses the padding spaces a full-screen program paints across the rest of the row. Leading indentation is left exactly as it is, so indented code, a `git log` message body and `git diff` context lines paste back the way they looked on screen. An `Alt+drag` rectangular selection is copied exactly as it looks, so its columns stay lined up.
 
 ## Everything else