Notify lifecycle extensions of compaction usage limits (#49097)

## Why

Usage-limit failures during manual or post-turn compaction did not notify turn lifecycle extensions, leaving them unable to react to these errors.

## What changed

Emit the turn error lifecycle notification for `UsageLimitExceeded` in both compaction paths. Preserve the completed answer after post-turn compaction fails, and avoid duplicating the error already emitted by manual compaction.

GitOrigin-RevId: f31155e5991d762a0779030921aedbd1f818cfbb

codex-rs/core/src/session/turn.rs

@@ -736,6 +736,12 @@ pub(crate) async fn run_turn(
                         ) {
                             return Err(err);
                         }
+                        let error = err.to_codex_protocol_error();
+                        if matches!(error, CodexErrorInfo::UsageLimitExceeded) {
+                            // Preserve the completed answer while stopping automatic work.
+                            sess.emit_turn_error_lifecycle(turn_context.as_ref(), error)
+                                .await;
+                        }
                         warn!(error = %err, "Post-turn compaction failed; preserving the completed turn");
                     }
                     break;

codex-rs/core/src/tasks/compact.rs

@@ -10,6 +10,7 @@ use crate::state::TaskKind;
 use codex_features::Feature;
 use codex_model_provider::RemoteCompactionSupport;
 use codex_protocol::error::CodexErrorDetails;
+use codex_protocol::protocol::CodexErrorInfo;
 use codex_protocol::user_input::UserInput;
 use tokio_util::sync::CancellationToken;
 
@@ -45,7 +46,8 @@ impl SessionTask for CompactTask {
                     "remote_v2",
                     /*manual*/ true,
                 );
-                crate::compact_remote_v2::run_remote_compact_task(session.clone(), ctx).await
+                crate::compact_remote_v2::run_remote_compact_task(session.clone(), Arc::clone(&ctx))
+                    .await
             }
             RemoteCompactionSupport::Unsupported => {
                 emit_compact_metric(
@@ -63,13 +65,18 @@ impl SessionTask for CompactTask {
                     // Compaction prompt is synthesized; no UI element ranges to preserve.
                     text_elements: Vec::new(),
                 }];
-                crate::compact::run_compact_task(session.clone(), ctx, input).await
+                crate::compact::run_compact_task(session.clone(), Arc::clone(&ctx), input).await
             }
         };
-        if let Err(err) = result
-            && matches!(err.details(), CodexErrorDetails::TurnAborted)
-        {
-            return Err(err);
+        if let Err(err) = result {
+            if matches!(err.details(), CodexErrorDetails::TurnAborted) {
+                return Err(err);
+            }
+            let error = err.to_codex_protocol_error();
+            if matches!(error, CodexErrorInfo::UsageLimitExceeded) {
+                // Compaction already emitted the error; notify extensions without emitting it twice.
+                session.emit_turn_error_lifecycle(ctx.as_ref(), error).await;
+            }
         }
         Ok(None)
     }