Add SessionEnd hooks for thread teardown (#33895)

## 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

codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__hooks_popup_shows_list_diagnostics.snap

@@ -16,6 +16,7 @@ expression: popup
   PreCompact            0           0           Before context compaction
   PostCompact           0           0           After context compaction
   SessionStart          0           0           When a new session starts
+  SessionEnd            0           0           Right before a session ends
   UserPromptSubmit      0           0           When the user submits a prompt
   SubagentStart         0           0           When a subagent is created
   SubagentStop          0           0           Right before a subagent ends its turn

codex-rs/tui/src/chatwidget/tests/helpers.rs

@@ -1686,6 +1686,7 @@ fn hook_event_label(event_name: codex_app_server_protocol::HookEventName) -> &'s
         codex_app_server_protocol::HookEventName::PreCompact => "PreCompact",
         codex_app_server_protocol::HookEventName::PostCompact => "PostCompact",
         codex_app_server_protocol::HookEventName::SessionStart => "SessionStart",
+        codex_app_server_protocol::HookEventName::SessionEnd => "SessionEnd",
         codex_app_server_protocol::HookEventName::UserPromptSubmit => "UserPromptSubmit",
         codex_app_server_protocol::HookEventName::SubagentStart => "SubagentStart",
         codex_app_server_protocol::HookEventName::SubagentStop => "SubagentStop",