## What changed
- Add the top-level `thread_unload_delay_secs` configuration key for the
app-server, with a 60-second default instead of the previous 30-minute
fixed delay.
- Allow zero-delay unloading and reject values that cannot fit in a
monotonic-clock deadline.
- Reset the unload countdown when a thread gains a subscriber or becomes
active, and preserve active turns even when the configured delay is zero.
- Document that unloading ephemeral threads discards their in-memory state.
## Testing
- Cover configuration parsing, defaults, overrides, and overflow rejection.
- Cover unsubscribe, resubscribe, delayed and immediate unloading,
notifications, persisted-thread resume, and WebSocket disconnect behavior.
GitOrigin-RevId: edd46f6b49bbdafbf606bff74378e8f569e95977
Eric Traut
5e26f7621c