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>

test/keyboard-shortcuts.test.ts

@@ -67,9 +67,14 @@ describe('keyboard shortcuts', () => {
     // selects real padding spaces, so the raw text is truthy and testing it would
     // spend the press on a copy of nothing — the same lost interrupt this test
     // guards, reached by a different door.
-    expect(terminalUiSource).toMatch(/const selection = this\.cleanedTerminalSelection\(\);/);
+    //
+    // The RAW selection is what travels on, because copyTerminalSelection cleans
+    // again on its own and the margin strip is not idempotent. Passing the
+    // cleaned string dedented every claude and codex copy twice; see
+    // test/terminal-copy-clean.test.ts for the branch's own pin.
+    expect(terminalUiSource).toMatch(/const selection = this\.cleanedTerminalSelection\(raw\);/);
     expect(terminalUiSource).toMatch(/if \(selection\.trim\(\)\) \{/);
-    expect(terminalUiSource).toContain('void this.copyTerminalSelection(selection);');
+    expect(terminalUiSource).toContain('void this.copyTerminalSelection(raw);');
     expect(appSource).toContain("id: 'copy-selection'");
   });
 

test/terminal-copy-clean.test.ts

@@ -407,7 +407,7 @@ describe('copyStripMargin — the per-device toggle', () => {
     // toggle is checked first. There is no buffer to read: the width is declared.
     const h = loadHarness({ copyStripMargin: false });
     select(h);
-    expect(h.app._activeCliGutterColumns()).toBe(0);
+    expect(h.app._cliGutterColumns()).toBe(0);
     expect(h.app.cleanedTerminalSelection()).toBe(body);
   });
 
@@ -455,7 +455,7 @@ describe('the gutter is DECLARED by the CLI, never measured off the pane', () =>
   it('takes the declared width off a mode that declares one', () => {
     const { app, setSelection } = loadHarness();
     setSelection(body, { mode: 'claude', from: 1, to: 2 });
-    expect(app._activeCliGutterColumns()).toBe(2);
+    expect(app._cliGutterColumns()).toBe(2);
     expect(app.cleanedTerminalSelection()).toBe(flush);
   });
 
@@ -466,14 +466,14 @@ describe('the gutter is DECLARED by the CLI, never measured off the pane', () =>
     // indents were 0, 2, 4, 6 and 8 at every one, never 1.
     const { app, setSelection } = loadHarness();
     setSelection('  terminal:\n    pane:\n      gutter:\n        width: 1', { mode: 'codex', from: 1, to: 4 });
-    expect(app._activeCliGutterColumns()).toBe(2);
+    expect(app._cliGutterColumns()).toBe(2);
     expect(app.cleanedTerminalSelection()).toBe('terminal:\n  pane:\n    gutter:\n      width: 1');
   });
 
   it('leaves a mode nobody has measured alone, because it declares none', () => {
     const { app, setSelection } = loadHarness();
     setSelection('    build:\n      steps:', { mode: 'opencode', from: 1, to: 2 });
-    expect(app._activeCliGutterColumns()).toBe(0);
+    expect(app._cliGutterColumns()).toBe(0);
     expect(app.cleanedTerminalSelection()).toBe('    build:\n      steps:');
   });
 
@@ -488,7 +488,7 @@ describe('the gutter is DECLARED by the CLI, never measured off the pane', () =>
     // the injection: no session gets a strip rather than every session guessing.
     const { app, setSelection } = loadHarness(undefined, null);
     setSelection(body, { mode: 'claude', from: 1, to: 2 });
-    expect(app._activeCliGutterColumns()).toBe(0);
+    expect(app._cliGutterColumns()).toBe(0);
     expect(app.cleanedTerminalSelection()).toBe(body);
   });
 
@@ -496,7 +496,7 @@ describe('the gutter is DECLARED by the CLI, never measured off the pane', () =>
     for (const bad of [0, -2, 2.5, '2', null] as unknown[]) {
       const { app, setSelection } = loadHarness(undefined, { claude: bad } as Record<string, number>);
       setSelection(body, { mode: 'claude', from: 1, to: 2 });
-      expect(app._activeCliGutterColumns()).toBe(0);
+      expect(app._cliGutterColumns()).toBe(0);
     }
   });
 
@@ -534,7 +534,7 @@ describe('the transcriptGutter capability, as the registry and server carry it',
     // The frontend looks the mode up in that map; the helper holds no id itself.
     const terminalUi = read('terminal-ui.js');
     const helper = terminalUi.slice(
-      terminalUi.indexOf('_activeCliGutterColumns() {'),
+      terminalUi.indexOf('_cliGutterColumns(sessionId) {'),
       terminalUi.indexOf('async copyTerminalSelection')
     );
     expect(helper).toContain('window.__codemanTranscriptGutter');
@@ -606,6 +606,56 @@ describe('copyTerminalSelection — what reaches the clipboard', () => {
       expect(terminal.clearSelection).toHaveBeenCalledTimes(1);
     });
   });
+
+  // Every case above runs on the harness default mode, which declares no gutter,
+  // so none of them can see a margin stripped twice. These two run on a mode that
+  // declares one.
+  it('takes the declared width off a claude pane exactly once', () => {
+    const { app, setSelection } = loadHarness();
+    setSelection('      fix(terminal): trim it', { mode: 'claude', from: 1, to: 2 });
+    return app.copyTerminalSelection().then(() => {
+      // 2 gutter columns off a body that carries 4 of its own.
+      expect(app._copyText).toHaveBeenCalledWith('    fix(terminal): trim it');
+    });
+  });
+
+  it("keeps a nested block's own indentation on a claude pane", () => {
+    const { app, setSelection } = loadHarness();
+    setSelection('    build:\n      steps:\n        - run: npm ci', { mode: 'claude', from: 1, to: 4 });
+    return app.copyTerminalSelection().then(() => {
+      expect(app._copyText).toHaveBeenCalledWith('  build:\n    steps:\n      - run: npm ci');
+    });
+  });
+});
+
+describe('the margin strip is not idempotent, so no caller may clean twice', () => {
+  // The trailing trim is a fixed point, and copyTerminalSelection leaned on that
+  // by re-cleaning whatever it was handed. The margin strip broke it: it takes
+  // the narrower of the declared width and the run every line shares, so a
+  // second pass takes up to `margin` columns more. Ctrl+C cleaned to decide
+  // whether to copy and then passed the CLEANED string on, which dedented every
+  // claude and codex copy twice on the most-used copy path of the four.
+  it('takes more off a block that has already been stripped', () => {
+    const h = loadHarness();
+    const clean = h.windowRef.CodemanCopySelection.clean;
+    const once = clean('      fix(terminal): trim it', { margin: 2 });
+    expect(once).toBe('    fix(terminal): trim it');
+    expect(clean(once, { margin: 2 })).toBe('  fix(terminal): trim it');
+  });
+
+  it('is pinned in the Ctrl+C branch, which gates on the clean and copies the raw', () => {
+    // The branch lives inside initTerminal's attachCustomKeyEventHandler closure,
+    // over a real xterm this harness cannot build, so the rule is pinned at the
+    // source rather than driven by a keystroke.
+    const terminalUi = read('terminal-ui.js');
+    const branch = terminalUi.slice(
+      terminalUi.indexOf('if (this.shouldCopyTerminalSelectionFromShortcut?.(ev)) {'),
+      terminalUi.indexOf('// Session-sidebar toggle chord')
+    );
+    expect(branch).toContain('const selection = this.cleanedTerminalSelection(raw);');
+    expect(branch).toContain('void this.copyTerminalSelection(raw);');
+    expect(branch).not.toContain('this.copyTerminalSelection(selection)');
+  });
 });
 
 describe('_flushAutoCopySelection — cleaned text is what Auto Copy handles', () => {