fix(browser): clean up owned browser daemons on shutdown after cancellation

Shutdown cleanup must not depend on active record.session capability,
which is cleared on cancellation. Guard cleanup by socket directory
presence so all owned daemons are terminated.

src/agent_tools/web_tools.py

@@ -2708,8 +2708,7 @@ async def shutdown_private_browser_sessions() -> None:
         _ACTIVE_BROWSER_SESSIONS.discard(session)
     from src.browser_identity import _REGISTRY
     for record in tuple(_REGISTRY.values()):
-        session = record.session
-        if session is not None and session.observation.daemon.owned():
+        if record.env and "AGENT_BROWSER_SOCKET_DIR" in record.env:
             browser_lifecycle.force_cleanup(Path(record.env["AGENT_BROWSER_SOCKET_DIR"]), record.key,
                 method="shutdown", pid_alive=lambda pid: _process_is_alive(pid))
         record.invalidate()