Session close and server shutdown leave session-scoped resources alive

Problem

Several session-scoped resources are only released by explicit per-resource close paths or full process disposal. When a session is archived or the daemon/server shuts down, live sessions and related server-side state can remain active longer than intended.

Observed cleanup gaps:

• server shutdown disposes the DI graph without first closing live agent sessions
• terminal records and pty processes are not cleaned up when a session closes
• filesystem watcher entries are not disposed when a session closes
• WebSocket broadcast per-session buffers, journal state, and in-flight turn tracking are not removed when a session closes
• tool-call start timestamps can remain after interrupted/aborted turns

Expected behavior

Session archive and server shutdown should use the normal session/resource cleanup paths so session-owned processes, watchers, buffers, journals, and turn bookkeeping are released promptly.

Proposed fix

• add a bulk live-session close path and call it during server shutdown before DI disposal
• subscribe session-scoped services to session close events
• drop per-session terminal, fs watcher, and WebSocket broadcast state on close
• clear tool-call timing state on turn boundaries/abort paths

Scope

This issue is limited to session lifecycle cleanup. Longer-term retention policies for completed background tasks/subagents and unrelated timeout hardening can be handled in separate follow-ups.

Trace the session archive/close path and the server shutdown path first, then inspect the session-owned terminal, pty, filesystem watcher, WebSocket broadcast, journal, and turn-tracking state described in the issue. Verify that shutdown closes live sessions before DI disposal and that session close removes all listed resources, including tool-call timing state after aborts.