Track compaction time in turn profiles (#34835)

## What changed

- Add `compaction_ms` to turn profile facts and turn analytics events.
- Measure manual and automatic compaction as an exclusive profile phase instead of including it in surrounding idle time.
- Complete the profile and total turn duration from the same instant so their elapsed times remain consistent.

## Testing

- Cover compaction phase accounting and profile-duration consistency.
- Update turn event serialization coverage for `compaction_ms`.

GitOrigin-RevId: 50f0e1cf19789a807f9f56c2ef763c620a5d641c

codex-rs/analytics/src/analytics_client_tests.rs

@@ -441,9 +441,10 @@ fn sample_turn_profile() -> TurnProfile {
     TurnProfile {
         before_first_sampling_ms: 100,
         sampling_ms: 700,
+        compaction_ms: 40,
         between_sampling_overhead_ms: 50,
         tool_blocking_ms: 250,
-        after_last_sampling_ms: 134,
+        after_last_sampling_ms: 94,
         sampling_request_count: 2,
         sampling_retry_count: 1,
     }
@@ -4065,9 +4066,10 @@ fn turn_event_serializes_expected_shape() {
             total_tokens: None,
             before_first_sampling_ms: 100,
             sampling_ms: 700,
+            compaction_ms: 40,
             between_sampling_overhead_ms: 50,
             tool_blocking_ms: 250,
-            after_last_sampling_ms: 134,
+            after_last_sampling_ms: 94,
             sampling_request_count: 2,
             sampling_retry_count: 1,
             duration_ms: Some(1234),
@@ -4138,9 +4140,10 @@ fn turn_event_serializes_expected_shape() {
                 "total_tokens": null,
                 "before_first_sampling_ms": 100,
                 "sampling_ms": 700,
+                "compaction_ms": 40,
                 "between_sampling_overhead_ms": 50,
                 "tool_blocking_ms": 250,
-                "after_last_sampling_ms": 134,
+                "after_last_sampling_ms": 94,
                 "sampling_request_count": 2,
                 "sampling_retry_count": 1,
                 "duration_ms": 1234,