fix(tui): sweep an attach status bar a killed terminal left behind

restore() runs after spawnSync returns, which covers detaching and the agent
exiting inside the pane, but not the terminal dying while attached. Closing the
window or dropping the SSH kills the TUI where it stands, and the bar it
installed stays pinned on the session: the next attach wears a stale bar naming
a different session, and the pane is a row shorter for good. Seen on the beta,
where the tester closed the window instead of detaching.

One sweep at startup, fire-and-forget so it can neither delay the first frame
nor fail a start. Only a bar carrying our own marker is touched, and the marker
is now the single source of the bar's own wording so the two cannot drift; a
user's hand-written status bar on the same session is left exactly as it is.
The session goes back to `status off`, which is how Codeman creates every pane
it owns and the only state this bar is ever applied over.

src/tui/tui-app.ts

@@ -55,6 +55,7 @@ import { approvalAnswerForKey, newApprovalIds } from './tui-approvals.js';
 import { composerScroll, composerStep, composerText, createComposer, type TuiComposerState } from './tui-composer.js';
 import { formatAwayDigest } from './tui-digest.js';
 import {
+  ATTACH_BANNER_MARKER,
   TuiClient,
   type TuiApprovalAnswer,
   type TuiEventStream,
@@ -316,7 +317,7 @@ export function buildAttachBanner(options: {
   return {
     status: 'on',
     'status-style': 'bg=default,fg=default',
-    'status-format[0]': `#[align=left] press #[bold]${chord}#[nobold] to detach, back to the codeman dashboard${right}#[default]`,
+    'status-format[0]': `#[align=left] press #[bold]${chord}#[nobold] to detach, ${ATTACH_BANNER_MARKER}${right}#[default]`,
   };
 }
 
@@ -981,6 +982,10 @@ class TuiApp {
     await this.refresh();
     if (server) this.subscribe();
 
+    // Fire and forget: a bar stranded by a previous run is cosmetic, so it must
+    // never delay the first frame or fail a start.
+    void this.client.clearLeakedAttachBanners().catch(() => undefined);
+
     return new Promise<number>((resolve) => {
       this.resolveExit = resolve;
     });