feat(tui): add web server auto-start, shell mode, and feature parity

TUI now checks if web server is running on startup and offers to start
it in the background. Added new CLI options: --with-web (auto-start),
--no-web (skip check), -p (port).

TUI feature parity with web interface:
- Shell mode: press 'h' in cases view to start bash instead of Claude
- Multi-start: press 'm' to start 1-20 sessions at once
- Respawn toggle: Ctrl+R to enable/disable respawn on Claude sessions
- Session rename: API support via useSessionManager hook

Security fixes from previous analysis:
- Command injection prevention in screen-manager.ts
- Path traversal protection in server.ts
- Input validation for shell-interpolated values

Also fixes memory leak in session.ts (timer tracking) and flaky test
timeout in session-cleanup.test.ts.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

test/session-cleanup.test.ts

@@ -101,7 +101,7 @@ describe('Session Cleanup', () => {
       for (const id of sessionIds) {
         expect(sessions.find((s: any) => s.id === id)).toBeUndefined();
       }
-    });
+    }, 60000); // Extended timeout for multi-session test
   });
 
   describe('Respawn Controller Cleanup', () => {