## Why
Goal creation and completion are moving through the goal extension, but
the rest of Codex still observes goal state through `ThreadGoalUpdated`
events. Without an event from the extension-owned tool path, a
model-initiated `create_goal` or `update_goal` can mutate the backend
and return a tool result while app-server and TUI listeners miss the
goal state transition.
## What changed
- Added `GoalEventEmitter` as a small wrapper around the host
`ExtensionEventSink` to build `EventMsg::ThreadGoalUpdated` events for
goal updates.
- Threaded the registry event sink into `GoalExtension` and the
`GoalToolExecutor`s created by the extension. The public
`GoalExtension::new` constructor keeps a `NoopExtensionEventSink`
fallback for standalone use.
- Emitted a goal update after successful `create_goal` and `update_goal`
tool calls. Until `ToolCall` exposes the current turn submission id,
these events use the tool call id as the event id and leave `turn_id`
unset.
Relevant code:
-
[`GoalEventEmitter::thread_goal_updated`](1fe2d73890/codex-rs/ext/goal/src/events.rs (L19-L32))
- [`GoalToolExecutor` emission
points](1fe2d73890/codex-rs/ext/goal/src/tool.rs (L161-L190))
## Testing
- `cargo test -p codex-goal-extension`
## Why
Extension lifecycle hooks sit on the host/extension boundary, but the
current trait surface only allows synchronous callbacks. That forces
extensions that need to seed, rehydrate, observe, or flush
extension-owned state during thread and turn transitions to either block
inside the callback or move async work into separate host plumbing.
This PR makes those lifecycle callbacks awaitable so extension
implementations can perform async work directly at the lifecycle point
where the host already has the relevant session, thread, or turn stores
available.
## What changed
- Makes `ThreadLifecycleContributor` and `TurnLifecycleContributor`
async in `codex-extension-api`.
- Awaits thread start/resume/stop and turn start/stop/abort lifecycle
callbacks from `codex-core`.
- Updates the guardian and memories extensions to implement the async
lifecycle trait surface.
- Updates the existing lifecycle tests to use async contributor
implementations.
- Adds `async-trait` to the crates that now expose or implement these
async object-safe lifecycle traits.
## Testing
- Existing `codex-core` lifecycle tests were updated to cover async
implementations for thread stop and turn abort ordering.
