Wire app-server extension event sink (#24586)

## Why

The goal extension already emits `ThreadGoalUpdated` events, but
production app-server thread extensions were built with the default
no-op extension event sink. That meant extension-driven goal updates
could be produced without ever reaching app-server clients.

## What changed

- Build app-server thread extensions with a host-provided
`ExtensionEventSink`.
- Add an app-server sink that converts extension `ThreadGoalUpdated`
events into `ServerNotification::ThreadGoalUpdated` broadcasts.
- Use the existing bounded outgoing message channel via `try_send` so
event forwarding cannot create an unbounded queue.
- Pass `NoopExtensionEventSink` in app-server tests that construct a
`ThreadManager` without an app-server host.
- Refresh `Cargo.lock` for the existing `codex-memories-extension`
`codex-otel` dependency.

## Verification

- `just test -p codex-app-server
extensions::tests::app_server_event_sink_forwards_thread_goal_updates`

codex-rs/app-server/src/message_processor.rs

@@ -8,6 +8,7 @@ use crate::attestation::app_server_attestation_provider;
 use crate::config_manager::ConfigManager;
 use crate::connection_rpc_gate::ConnectionRpcGate;
 use crate::error_code::invalid_request;
+use crate::extensions::app_server_extension_event_sink;
 use crate::extensions::guardian_agent_spawner;
 use crate::extensions::thread_extensions;
 use crate::fs_watch::FsWatchManager;
@@ -310,7 +311,10 @@ impl MessageProcessor {
                 auth_manager.clone(),
                 session_source,
                 environment_manager,
-                thread_extensions(guardian_agent_spawner(thread_manager.clone())),
+                thread_extensions(
+                    guardian_agent_spawner(thread_manager.clone()),
+                    app_server_extension_event_sink(outgoing.clone()),
+                ),
                 Some(analytics_events_client.clone()),
                 Arc::clone(&thread_store),
                 state_db.clone(),