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/app-server-protocol/src/protocol/v2/config.rs

@@ -441,6 +441,9 @@ pub struct ManagedHooksRequirements {
     #[serde(rename = "SessionStart")]
     #[ts(rename = "SessionStart")]
     pub session_start: Vec<ConfiguredHookMatcherGroup>,
+    #[serde(rename = "SessionEnd", default)]
+    #[ts(rename = "SessionEnd")]
+    pub session_end: Vec<ConfiguredHookMatcherGroup>,
     #[serde(rename = "UserPromptSubmit")]
     #[ts(rename = "UserPromptSubmit")]
     pub user_prompt_submit: Vec<ConfiguredHookMatcherGroup>,

codex-rs/app-server-protocol/src/protocol/v2/hook.rs

@@ -17,7 +17,7 @@ use ts_rs::TS;
 
 v2_enum_from_core!(
     pub enum HookEventName from CoreHookEventName {
-        PreToolUse, PermissionRequest, PostToolUse, PreCompact, PostCompact, SessionStart, UserPromptSubmit, SubagentStart, SubagentStop, Stop
+        PreToolUse, PermissionRequest, PostToolUse, PreCompact, PostCompact, SessionStart, SessionEnd, UserPromptSubmit, SubagentStart, SubagentStop, Stop
     }
 );