Add goal extension telemetry parity (#24615)

## Why

`core/src/goals.rs` already emits OTEL metrics for goal creation,
resume, terminal transitions, token counts, and duration. As `/goal`
moves into `ext/goal`, the extension needs to preserve that telemetry
contract instead of only emitting app-visible `ThreadGoalUpdated`
events.

This keeps the existing `codex.goal.*` metric surface intact while goal
lifecycle ownership shifts toward the extension.

## What changed

- Added an extension-local `GoalMetrics` helper that records the
existing `codex.goal.*` counters and histograms through `codex-otel`.
- Threaded an optional `MetricsClient` through `install_with_backend`,
`GoalExtension`, `GoalRuntimeHandle`, and `GoalToolExecutor`.
- Emitted created, resumed, and terminal goal metrics from the extension
paths that create goals, restore active goals on thread resume, account
budget limits, complete or block goals, and handle external goal
mutations.
- Updated existing goal extension test setup callsites to pass `None`
for metrics when instrumentation is not under test.

## Verification

Not run locally.

codex-rs/ext/goal/src/runtime.rs

@@ -11,6 +11,7 @@ use codex_protocol::protocol::ThreadGoal;
 use crate::accounting::BudgetLimitedGoalDisposition;
 use crate::accounting::GoalAccountingState;
 use crate::events::GoalEventEmitter;
+use crate::metrics::GoalMetrics;
 use crate::steering::objective_updated_steering_item;
 use crate::tool::protocol_goal_from_state;
 
@@ -23,6 +24,7 @@ struct GoalRuntimeInner {
     thread_id: ThreadId,
     state_dbs: Arc<codex_state::StateRuntime>,
     event_emitter: GoalEventEmitter,
+    metrics: GoalMetrics,
     thread_manager: Weak<ThreadManager>,
     accounting_state: Arc<GoalAccountingState>,
     enabled: AtomicBool,
@@ -61,6 +63,7 @@ impl GoalRuntimeHandle {
         thread_id: ThreadId,
         state_dbs: Arc<codex_state::StateRuntime>,
         event_emitter: GoalEventEmitter,
+        metrics: GoalMetrics,
         thread_manager: Weak<ThreadManager>,
         accounting_state: Arc<GoalAccountingState>,
         enabled: bool,
@@ -70,6 +73,7 @@ impl GoalRuntimeHandle {
                 thread_id,
                 state_dbs,
                 event_emitter,
+                metrics,
                 thread_manager,
                 accounting_state,
                 enabled: AtomicBool::new(enabled),
@@ -127,6 +131,21 @@ impl GoalRuntimeHandle {
             return Ok(());
         }
 
+        let replaced_existing_goal = previous_goal
+            .as_ref()
+            .is_some_and(|previous_goal| previous_goal.goal_id != goal.goal_id);
+        if previous_goal.is_none() || replaced_existing_goal {
+            self.inner.metrics.record_created();
+        }
+        let previous_status = previous_goal
+            .as_ref()
+            .and_then(|previous_goal| (!replaced_existing_goal).then_some(previous_goal.status));
+        self.inner
+            .metrics
+            .record_resumed_if_status_changed(previous_status, goal.status);
+        self.inner
+            .metrics
+            .record_terminal_if_status_changed(previous_status, &goal);
         let should_steer_active_turn = previous_goal.as_ref().is_none_or(|previous_goal| {
             previous_goal.goal_id != goal.goal_id
                 || previous_goal.status != codex_state::ThreadGoalStatus::Active
@@ -202,6 +221,9 @@ impl GoalRuntimeHandle {
         let Some(snapshot) = accounting.progress_snapshot(turn_id) else {
             return Ok(None);
         };
+        let previous_status = self
+            .current_goal_status_for_metrics(Some(snapshot.expected_goal_id.as_str()))
+            .await?;
         let outcome = self
             .inner
             .state_dbs
@@ -218,6 +240,9 @@ impl GoalRuntimeHandle {
         Ok(match outcome {
             codex_state::GoalAccountingOutcome::Updated(goal) => {
                 let goal_id = goal.goal_id.clone();
+                self.inner
+                    .metrics
+                    .record_terminal_if_status_changed(previous_status, &goal);
                 accounting.mark_progress_accounted_for_status(
                     turn_id,
                     &snapshot,
@@ -246,6 +271,9 @@ impl GoalRuntimeHandle {
         let Some(snapshot) = accounting.idle_progress_snapshot() else {
             return Ok(None);
         };
+        let previous_status = self
+            .current_goal_status_for_metrics(Some(snapshot.expected_goal_id.as_str()))
+            .await?;
         let outcome = self
             .inner
             .state_dbs
@@ -262,6 +290,9 @@ impl GoalRuntimeHandle {
         Ok(match outcome {
             codex_state::GoalAccountingOutcome::Updated(goal) => {
                 let goal_id = goal.goal_id.clone();
+                self.inner
+                    .metrics
+                    .record_terminal_if_status_changed(previous_status, &goal);
                 accounting.mark_idle_progress_accounted_for_status(
                     &snapshot,
                     goal.status,
@@ -281,4 +312,22 @@ impl GoalRuntimeHandle {
             }
         })
     }
+
+    async fn current_goal_status_for_metrics(
+        &self,
+        expected_goal_id: Option<&str>,
+    ) -> Result<Option<codex_state::ThreadGoalStatus>, String> {
+        let goal = self
+            .inner
+            .state_dbs
+            .thread_goals()
+            .get_thread_goal(self.thread_id())
+            .await
+            .map_err(|err| err.to_string())?;
+        Ok(goal.and_then(|goal| {
+            expected_goal_id
+                .is_none_or(|expected_goal_id| goal.goal_id == expected_goal_id)
+                .then_some(goal.status)
+        }))
+    }
 }