Honor thread analytics opt-outs when using shared clients (#44646)

## Why

An enabled shared analytics client could override a thread's explicit opt-out.
Delegated threads also emitted initialization events through the parent's client,
bypassing the child's analytics setting.

## What changed

- Use a disabled analytics client when `config.analytics_enabled` is `Some(false)`,
  without disabling analytics for sibling threads or overriding a disabled host client.
- Emit delegated thread initialization events through the child's analytics client.
- Expose the effective analytics state through `CodexThread::analytics_enabled()`.

## Testing

Add regression tests for explicit and unset thread settings with enabled, disabled,
and absent shared clients, plus delegated child opt-outs with an enabled parent.
Update compaction and rollout-budget rollback tests to wait for thread idle after
turn completion and fail immediately on rollback errors.

GitOrigin-RevId: 547852909af1a6822b95c0bcd2336b0d6bc7aad1

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

@@ -1438,13 +1438,17 @@ impl Session {
                 });
             }
 
-            let analytics_events_client = analytics_events_client.unwrap_or_else(|| {
-                AnalyticsEventsClient::new(
-                    Arc::clone(&auth_manager),
-                    config.chatgpt_base_url.trim_end_matches('/').to_string(),
-                    config.analytics_enabled,
-                )
-            });
+            let analytics_events_client = if config.analytics_enabled == Some(false) {
+                AnalyticsEventsClient::disabled()
+            } else {
+                analytics_events_client.unwrap_or_else(|| {
+                    AnalyticsEventsClient::new(
+                        Arc::clone(&auth_manager),
+                        config.chatgpt_base_url.trim_end_matches('/').to_string(),
+                        config.analytics_enabled,
+                    )
+                })
+            };
             for item in initial_history.get_rollout_items() {
                 match item {
                     RolloutItem::Compacted(compacted) => {