fix: apply the review items for #688 at merge

disarmTuiSwitchGuard matches the closed `#{client_tty},<tty>}` form, so a TUI on /dev/pts/4 no longer removes the hook armed for a second TUI on /dev/pts/41 (unit test plus a real-tmux case)
beginAttachHandoff arms the one-shot attach hook as its last tmux call before spawnSync, after the switch keys and the per-session dressing loop, with an order assertion in tui-app.test.ts and a sentence in the invariants paragraph
docs/remote-sessions.md and the buildRemoteLaunchCommand JSDoc show `remain-on-exit failed` at the end of the remote create chain

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

test/tui/tui-app.test.ts

@@ -638,6 +638,8 @@ describe('attach switch keys stay on the TUI client', () => {
     const unbinds: Array<{ key: string; owner: string | undefined }> = [];
     let armed: string | null = null;
     let disarmed: string | null = null;
+    // tmux calls in order, to pin where the attach hook is armed.
+    const order: string[] = [];
     const client = {
       readPrefixKey: async () => 'C-b',
       readDetachKey: async () => 'd',
@@ -645,6 +647,7 @@ describe('attach switch keys stay on the TUI client', () => {
       bindDetachKey: async () => true,
       unbindDetachKey: async () => true,
       armTuiSwitchGuard: async (tty: string) => {
+        order.push('arm');
         armed = tty;
         return true;
       },
@@ -652,6 +655,7 @@ describe('attach switch keys stay on the TUI client', () => {
         disarmed = tty;
       },
       bindSwitchKey: async (key: string, target: string, tty: string) => {
+        order.push('bind');
         binds.push({ key, target, tty });
         return true;
       },
@@ -659,11 +663,17 @@ describe('attach switch keys stay on the TUI client', () => {
         unbinds.push({ key, owner });
       },
       readSessionOptions: async () => null,
-      applySessionOptions: async () => true,
+      applySessionOptions: async () => {
+        order.push('dress');
+        return true;
+      },
       restoreSessionOptions: async () => true,
       readWindowSizing: async () => null,
       presizeWindow: async () => true,
-      followAttachingClient: async () => true,
+      followAttachingClient: async () => {
+        order.push('follow');
+        return true;
+      },
       restoreWindowSizing: async () => true,
     } as unknown as TuiClient;
 
@@ -681,6 +691,10 @@ describe('attach switch keys stay on the TUI client', () => {
       '/dev/pts/4'
     );
     expect(armed).toBe('/dev/pts/4');
+    // Armed once, as the LAST tmux call of the handoff: a TUI killed while the
+    // bars were being dressed must not leave a one-shot hook for its tty that a
+    // browser tab's attach on a reused pty would fire.
+    expect(order).toEqual(['bind', 'bind', 'dress', 'follow', 'dress', 'arm']);
     expect(binds).toEqual([
       { key: 'M-1', target: 'codeman-aaaa1111', tty: '/dev/pts/4' },
       { key: 'M-2', target: 'codeman-bbbb2222', tty: '/dev/pts/4' },

test/tui/tui-client.test.ts

@@ -690,6 +690,27 @@ describe('TUI switch-key guard', () => {
     expect(hook).toContain('\\#{client_pid}');
     expect(hook).toContain('set-hook -gu client-attached[90]');
   });
+
+  it('disarms only the hook armed for its own tty, not one for a tty it is a prefix of', async () => {
+    // `/dev/pts/4` is a substring of `/dev/pts/41`: a bare includes() removed a
+    // second TUI's hook and left its Alt keys dead for that attach.
+    const disarm = async (armedFor: string, ownTty: string): Promise<string[][]> => {
+      const calls: string[][] = [];
+      const exec: TuiExecFile = async (_file, args) => {
+        calls.push([...args]);
+        if (args.includes('show-hooks')) {
+          return { stdout: `client-attached[90] ${tuiSwitchAttachHook(armedFor)}\n`, stderr: '' };
+        }
+        return { stdout: '', stderr: '' };
+      };
+      await new TuiClient({ baseUrl, socket: 'codeman-beta', exec }).disarmTuiSwitchGuard(ownTty);
+      return calls.filter((args) => args.includes('set-hook'));
+    };
+    expect(await disarm('/dev/pts/41', '/dev/pts/4')).toEqual([]);
+    expect(await disarm('/dev/pts/4', '/dev/pts/4')).toEqual([
+      ['-L', 'codeman-beta', 'set-hook', '-gu', 'client-attached[90]'],
+    ]);
+  });
 });
 
 describe('parsePrefixBinding', () => {

test/tui/tui-switch-guard.test.ts

@@ -154,7 +154,9 @@ describe.skipIf(!hasTmux)('TUI M-1..M-9 switch only the attaching client', () =>
     expect(await client.armTuiSwitchGuard(tty)).toBe(true);
     const hooks = run(['show-hooks', '-g']);
     expect(hooks).toContain('client-attached[90]');
-    expect(hooks).toContain(tty);
+    // The closed form, as stored: disarmTuiSwitchGuard matches on it, so a
+    // hook for /dev/pts/41 is not taken for /dev/pts/4's.
+    expect(hooks).toContain(`#{client_tty},${tty}}`);
     // The stored hook still names the format. Expanding it while the hook is
     // stored would save an empty pid (no client yet) and the guard would never match.
     expect(hooks).toContain('#{client_pid}');
@@ -226,5 +228,14 @@ describe.skipIf(!hasTmux)('TUI M-1..M-9 switch only the attaching client', () =>
     await client.disarmTuiSwitchGuard(tty);
     expect(run(['list-keys', '-T', 'root'])).not.toContain(`switch-client -t ${beta}`);
     expect(() => run(['show-options', '-gv', '@codeman-tui-pid'])).toThrow();
+
+    // A hook armed for a tty this one is a prefix of (pts/4 vs pts/41) is
+    // another TUI's, and this tty's disarm must leave it.
+    const longer = `${tty}1`;
+    expect(await client.armTuiSwitchGuard(longer)).toBe(true);
+    await client.disarmTuiSwitchGuard(tty);
+    expect(run(['show-hooks', '-g'])).toContain('client-attached[90]');
+    await client.disarmTuiSwitchGuard(longer);
+    expect(run(['show-hooks', '-g'])).not.toContain('client-attached[90]');
   });
 });