Defer persistence of rollout file (#11028)

- Defer rollout persistence for fresh threads (`InitialHistory::New`):
keep rollout events in memory and only materialize rollout file + state
DB row on first `EventMsg::UserMessage`.
- Keep precomputed rollout path available before materialization.
- Change `thread/start` to build thread response from live config
snapshot and optional precomputed path.
- Improve pre-materialization behavior in app-server/TUI: clearer
invalid-request errors for file-backed ops and a friendlier `/fork` “not
ready yet” UX.
- Update tests to match deferred semantics across
start/read/archive/unarchive/fork/resume/review flows.
- Improved resilience of user_shell test, which should be unrelated to
this change but must be affected by timing changes

For Reviewers:
* The primary change is in recorder.rs
* Most of the other changes were to fix up broken assumptions in
existing tests

Testing:
* Manually tested CLI
* Exercised app server paths by manually running IDE Extension with
rebuilt CLI binary
* Only user-visible change is that `/fork` in TUI generates visible
error if used prior to first turn

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

@@ -240,6 +240,7 @@ pub(crate) async fn exit_review_mode(
             }],
         )
         .await;
+
     session
         .send_event(
             ctx.as_ref(),
@@ -260,4 +261,9 @@ pub(crate) async fn exit_review_mode(
             },
         )
         .await;
+
+    // Review turns can run before any regular user turn, so explicitly
+    // materialize rollout persistence. Do this after emitting review output so
+    // file creation + git metadata collection cannot delay client-facing items.
+    session.ensure_rollout_materialized().await;
 }