Include shared histories in rollout compression (#42039)

## What changed

- Make `local_thread_store_compression` compress cold rollout files across shared and forked histories without a separate compression mode.
- Retire `local_thread_store_shared_compression` while continuing to accept it in strict configuration without changing compression behavior.
- Read rollout files through the compressed-rollout reader when `codex exec resume` determines the latest turn's working directory.

## Testing

- Cover compression and restoration of an archived fork chain.
- Cover cwd-based resume selection when only the compressed rollout remains.
- Cover the removed compatibility key in strict configuration.

GitOrigin-RevId: 8edebf61eccc1f79cabb8e641f8982c76f337bf1

codex-rs/features/src/lib.rs

@@ -171,9 +171,10 @@ pub enum Feature {
     MemoryTool,
     /// Enable importing project-scoped memory from external agents.
     ExternalAgentMemoryImport,
-    /// Compress cold local thread-store rollout files.
+    /// Compress cold local thread-store rollout files, including shared histories.
+    /// Requires every reader of the Codex home to support compressed shared histories.
     LocalThreadStoreCompression,
-    /// Allow rollout compression on homes used exclusively by compressed-lineage-aware readers.
+    /// Removed compatibility flag; local_thread_store_compression controls all rollout files.
     LocalThreadStoreSharedCompression,
     /// Migrate legacy local rollout files to paginated history in the background.
     BackgroundPaginatedRolloutMigration,
@@ -1081,7 +1082,7 @@ pub const FEATURES: &[FeatureSpec] = &[
     FeatureSpec {
         id: Feature::LocalThreadStoreSharedCompression,
         key: "local_thread_store_shared_compression",
-        stage: Stage::UnderDevelopment,
+        stage: Stage::Removed,
         default_enabled: false,
     },
     FeatureSpec {