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/local/mod.rs

@@ -305,7 +305,6 @@ mod tests {
 
     use super::*;
     use crate::LiveThread;
-    use crate::ThreadEventPersistenceMode;
     use crate::ThreadPersistenceMetadata;
     use crate::local::test_support::test_config;
     use crate::local::test_support::write_archived_session_file;
@@ -539,7 +538,6 @@ mod tests {
                     model_provider: "different-provider".to_string(),
                     memory_mode: ThreadMemoryMode::Enabled,
                 },
-                event_persistence_mode: ThreadEventPersistenceMode::Limited,
             },
         )
         .await
@@ -594,7 +592,6 @@ mod tests {
                     model_provider: "different-provider".to_string(),
                     memory_mode: ThreadMemoryMode::Enabled,
                 },
-                event_persistence_mode: ThreadEventPersistenceMode::Limited,
             },
         )
         .await
@@ -720,7 +717,6 @@ mod tests {
                 history: None,
                 include_archived: true,
                 metadata: thread_metadata(),
-                event_persistence_mode: ThreadEventPersistenceMode::Limited,
             })
             .await
             .expect("resume live thread");
@@ -781,7 +777,6 @@ mod tests {
                 history: None,
                 include_archived: true,
                 metadata: thread_metadata(),
-                event_persistence_mode: ThreadEventPersistenceMode::Limited,
             })
             .await
             .expect_err("duplicate live resume should fail");
@@ -808,7 +803,6 @@ mod tests {
                     model_provider: "test-provider".to_string(),
                     memory_mode: ThreadMemoryMode::Enabled,
                 },
-                event_persistence_mode: ThreadEventPersistenceMode::Limited,
             })
             .await
             .expect_err("missing cwd should fail");
@@ -834,7 +828,6 @@ mod tests {
                 history: None,
                 include_archived: true,
                 metadata: thread_metadata(),
-                event_persistence_mode: ThreadEventPersistenceMode::Limited,
             })
             .await
             .expect("resume live thread");
@@ -883,7 +876,6 @@ mod tests {
                 history: None,
                 include_archived: true,
                 metadata: thread_metadata(),
-                event_persistence_mode: ThreadEventPersistenceMode::Limited,
             })
             .await
             .expect("resume live thread");
@@ -922,7 +914,6 @@ mod tests {
                 history: None,
                 include_archived: true,
                 metadata: thread_metadata(),
-                event_persistence_mode: ThreadEventPersistenceMode::Limited,
             })
             .await
             .expect("resume live archived thread");
@@ -1029,7 +1020,6 @@ mod tests {
             base_instructions: BaseInstructions::default(),
             dynamic_tools: Vec::new(),
             metadata: thread_metadata(),
-            event_persistence_mode: ThreadEventPersistenceMode::Limited,
         }
     }