Preserve turn attribution across recovery and compaction (#51402)

## Why

Recovering an interrupted turn replaced its original trigger with `retry` and restored only its root lineage from model context. Turns suspended before that context was written could lose their attribution entirely.

## What changed

- Persist regular-turn attribution in `TurnStartedEvent` and compaction resume metadata, including the trigger, parent and root turn IDs, and initiating agent path.
- Restore matching attribution during recovery, keep unknown triggers absent, and retain the model-context root fallback for older records.
- Reconstruct attribution from surviving turns across rollback and late completion or abort events, and clear inherited attribution when spawning a forked agent.

## Testing

Add coverage for repeated cold recovery, suspension before context persistence, legacy rollouts, fresh attribution on subsequent turns, compaction checkpoints, rollback, and late terminal events.

GitOrigin-RevId: 85b5763e8fbd48a1ea2c07cfda8196e63c2cd33a

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

@@ -3089,6 +3089,7 @@ mod tests {
             state.track_current_turn_event(
                 "turn-1",
                 &EventMsg::TurnStarted(codex_protocol::protocol::TurnStartedEvent {
+                    turn_attribution: None,
                     turn_id: "turn-1".to_string(),
                     root_turn_id: None,
                     trace_id: None,
@@ -3125,6 +3126,7 @@ mod tests {
             Event {
                 id: "turn-1".to_string(),
                 msg: EventMsg::TurnStarted(codex_protocol::protocol::TurnStartedEvent {
+                    turn_attribution: None,
                     turn_id: "turn-1".to_string(),
                     root_turn_id: None,
                     trace_id: None,
@@ -3395,6 +3397,7 @@ mod tests {
             state.track_current_turn_event(
                 &event_turn_id,
                 &EventMsg::TurnStarted(codex_protocol::protocol::TurnStartedEvent {
+                    turn_attribution: None,
                     turn_id: event_turn_id.clone(),
                     root_turn_id: None,
                     trace_id: None,

codex-rs/app-server/src/request_processors/thread_processor_tests.rs

@@ -1199,6 +1199,7 @@ mod thread_processor_behavior_tests {
             state.track_current_turn_event(
                 "turn-1",
                 &EventMsg::TurnStarted(codex_protocol::protocol::TurnStartedEvent {
+                    turn_attribution: None,
                     turn_id: "turn-1".to_string(),
                     root_turn_id: None,
                     trace_id: None,

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

@@ -87,6 +87,7 @@ async fn handle_observes_only_matching_model_provider() {
     let event = Event {
         id: "turn-1".to_string(),
         msg: EventMsg::TurnStarted(TurnStartedEvent {
+            turn_attribution: None,
             turn_id: "turn-1".to_string(),
             root_turn_id: None,
             trace_id: None,