a commander is a commander wherever it is opened

Fixing a regression I introduced last night. Commander rows in the Live list were changed to open in /chat
rather than navigating to Command HQ — right, and it cost the composer its commander controls, because
`isCommander` was computed from the ROUTE: `manager.context === 'command-hq'`. So the same commander,
rendered on a different screen, silently lost "exit and hand back, then re-arm" — the only fire behaviour a
watcher wants, and the one the dialog makes default inside a commander.

GET /chat/sessions/:id now reports isCommander, derived from the session's own cwd by the same
isCommandersDir already used by the sessions list and /chat/live. The answer travels with the conversation.

The composer reads one value, manager.isCommander, true when EITHER source says so — and both are needed.
The screen knows when Command HQ starts a commander, before a session or a transcript exists for any route
to report on. The session knows once it does, wherever it is opened. Screen-only was this bug; session-only
would have broken the brand-new composer, which is where the whole thing starts.

Verified on a real commander rather than by reading: 172cdd8c resolves cwd=…/commanders and
isCommander=true.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/workspaces/state/src/useClaudeSessions.ts

@@ -96,6 +96,14 @@ export type ClaudeSessionDetail = {
   title?: string | null;
   /** Transcripts spliced into `messages` — `> 1` when this is a merged `/clear` chain. */
   partCount?: number;
+  /**
+   * A commander rather than an ordinary conversation, derived server-side from this session's own cwd.
+   *
+   * It travels with the SESSION and not with the screen, which is the whole point. The composer decides
+   * whether to offer "exit and hand back, then re-arm" — the only fire behaviour a watcher wants — and used
+   * to decide it from the route, so the same commander opened in /chat quietly lost it.
+   */
+  isCommander?: boolean;
 };
 
 export type ClaudePwd = { cwd: string; sessionCount: number; updatedAt: string; isDefault: boolean };