When the laptop sleeps and wakes, the WebSocket reconnects but the
gateway's in-memory session table is cleared. The desktop app still
holds the old activeSessionId, so the next prompt.submit call returns
error 4001 ('session not found'), surfaced to the user as:
'Prompt failed: session not found'
Fix: wrap prompt.submit in a try/catch. On 'session not found', call
session.resume with the durable SQLite session ID (selectedStoredSessionIdRef)
to re-register the session in the gateway, update activeSessionIdRef to
the fresh live session_id, then retry prompt.submit once.
If recovery fails or the error is unrelated, the original error is
re-thrown and surfaces normally.
72f522d464