app-server: remove experimental persist_extended_history bool flag (#25712)

## Summary

Remove the dead experimental `persistExtendedHistory` app-server flag
and collapse rollout persistence to the single policy app-server already
used.

## What Changed

- Removed `persistExtendedHistory` from v2 thread start/resume/fork
params and deleted its deprecation notice path.
- Removed the persistence-mode enums and plumbing through core, rollout,
and thread-store.
- Made rollout filtering mode-free, keeping the existing limited
persisted-history behavior.

## Test Plan

- `just write-app-server-schema`
- `cargo nextest run --no-fail-fast -p codex-app-server-protocol
schema_fixtures`
- `cargo nextest run --no-fail-fast -p codex-app-server
thread_shell_command_history_responses_exclude_persisted_command_executions`
- `cargo nextest run --no-fail-fast -p codex-rollout -p
codex-thread-store`
- final `rg` for removed flag/type names

codex-rs/thread-store/src/live_thread.rs

@@ -4,7 +4,6 @@ use std::sync::Arc;
 use codex_protocol::ThreadId;
 use codex_protocol::protocol::RolloutItem;
 use codex_protocol::protocol::ThreadMemoryMode;
-use codex_rollout::EventPersistenceMode;
 use codex_rollout::persisted_rollout_items;
 use tokio::sync::Mutex;
 use tracing::warn;
@@ -17,7 +16,6 @@ use crate::ReadThreadParams;
 use crate::ResumeThreadParams;
 use crate::StoredThread;
 use crate::StoredThreadHistory;
-use crate::ThreadEventPersistenceMode;
 use crate::ThreadMetadataPatch;
 use crate::ThreadStore;
 use crate::ThreadStoreResult;
@@ -33,7 +31,6 @@ use crate::thread_metadata_sync::ThreadMetadataSync;
 pub struct LiveThread {
     thread_id: ThreadId,
     thread_store: Arc<dyn ThreadStore>,
-    event_persistence_mode: EventPersistenceMode,
     metadata_sync: Arc<Mutex<ThreadMetadataSync>>,
 }
 
@@ -92,13 +89,11 @@ impl LiveThread {
         params: CreateThreadParams,
     ) -> ThreadStoreResult<Self> {
         let thread_id = params.thread_id;
-        let event_persistence_mode = event_persistence_mode(params.event_persistence_mode);
         let metadata_sync = ThreadMetadataSync::for_create(&params).await;
         thread_store.create_thread(params).await?;
         Ok(Self {
             thread_id,
             thread_store,
-            event_persistence_mode,
             metadata_sync: Arc::new(Mutex::new(metadata_sync)),
         })
     }
@@ -108,7 +103,6 @@ impl LiveThread {
         mut params: ResumeThreadParams,
     ) -> ThreadStoreResult<Self> {
         let thread_id = params.thread_id;
-        let event_persistence_mode = event_persistence_mode(params.event_persistence_mode);
         let should_load_history = params.history.is_none();
         let include_archived = params.include_archived;
         thread_store.resume_thread(params.clone()).await?;
@@ -131,13 +125,12 @@ impl LiveThread {
         Ok(Self {
             thread_id,
             thread_store,
-            event_persistence_mode,
             metadata_sync: Arc::new(Mutex::new(metadata_sync)),
         })
     }
 
     pub async fn append_items(&self, items: &[RolloutItem]) -> ThreadStoreResult<()> {
-        let canonical_items = persisted_rollout_items(items, self.event_persistence_mode);
+        let canonical_items = persisted_rollout_items(items);
         if canonical_items.is_empty() {
             return Ok(());
         }
@@ -301,10 +294,3 @@ impl LiveThread {
         Ok(())
     }
 }
-
-fn event_persistence_mode(mode: ThreadEventPersistenceMode) -> EventPersistenceMode {
-    match mode {
-        ThreadEventPersistenceMode::Limited => EventPersistenceMode::Limited,
-        ThreadEventPersistenceMode::Extended => EventPersistenceMode::Extended,
-    }
-}