## Why
Stdio shutdown can hang on open pipes or blocked I/O, and Unix `SIGTERM` needs to run connection cleanup so owned commands terminate and session-end hooks execute.
## What changed
- Handle `SIGTERM` on a dedicated signal thread and close the stdio connection through the existing cleanup path.
- Move blocking stdin and stdout operations to dedicated threads so they do not hold the Tokio runtime open. Cancel message forwarding on `SIGTERM` to release blocked producers.
- When shutdown signal handling is enabled on Unix, start a shared 45-second watchdog on EOF or `SIGTERM`. Preserve the first deadline and exit with status `1` if cleanup or runtime teardown stalls, even when logging is blocked.
## Testing
Add Unix integration coverage for shutdown with open pipes, blocked stdout, blocked stderr, and a stalled filesystem write. Verify command and child-process termination, preserve the EOF deadline when `SIGTERM` follows, and extend session-end hook coverage to `SIGTERM`.
GitOrigin-RevId: 43a80b8277eb50519cdc293eb3b5dc2cad00b3aa
## What changed
- Add typed helpers for initialized app-server instances, JSON-RPC requests,
responses, notifications, and thread startup.
- Add a composable `MockResponsesConfig` builder while preserving the existing
mock config writers.
- Migrate the app-server integration suite to the shared helpers, removing
repeated request ID management, deserialization, initialization, and config
assembly.
## Testing
- Add unit coverage for composing mock provider, feature, and extra config, and
for compatibility of the existing mock config writer.
GitOrigin-RevId: 62da177c1d6e8299400de64bd6766567bf1ba3d8
## What changed
- Add the `SessionEnd` hook event to hook configuration, protocol schemas, analytics, and the hooks browser.
- Run matching hooks for root threads during shutdown, including app-server archive, delete, idle unload, and graceful shutdown. Flush the transcript first and provide the session ID, transcript path, working directory, and `reason: "other"`.
- Keep teardown bounded: hook output is advisory, the default timeout is one second, configured timeouts are capped at three seconds, and async hooks run synchronously with a warning.
## Testing
- Cover transcript availability, matcher selection, timeout normalization, ignored control output, subagent exclusion, archive/delete ordering, and graceful shutdown of multiple loaded threads.
GitOrigin-RevId: 5d19a658677a137caf836ed5042dcb43f5eb6d1a
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