Sessiond caches the in-memory SessionManager and never re-reads the
session file. When the same session is also being edited by another
process (e.g. the pi CLI), new entries on disk are invisible to the
web UI \u2014 the tail of the conversation gets cut.
Add a manual Reload action in the session three-dot menu:
- Server: PiSessionService.reload(sessionId) closes the active
session and re-opens it from disk, then publishes a fresh status.
Exposed as POST /api/.../sessions/:sessionId/reload.
- Client: api.reloadSession, SessionController.reloadSession which
discards the cached transcript and re-runs selectSession so the
history page is re-fetched.
- ChatTranscriptStore gains discard(sessionId) and the history
cache adapter gains optional remove(sessionId).
- SessionList shows a Reload entry for non-archived, non-cached
sessions; plumbed through AppNavigationPanel and PiWebApp.
Note: pi-web-sessiond.service must be restarted manually after this
change since the session daemon code path is affected.
