Store turn skill state in extension data (#36740)

## What changed

- Store each turn's host skills snapshot in `ExtensionData` and expose it through
  `TurnContext::skills_snapshot`.
- Lazily keep implicit skill invocation deduplication state in the same turn-scoped
  store.
- Carry the skills snapshot into review turns without a separate
  `TurnSkillsContext` field.

GitOrigin-RevId: d71579b5d230bd0b5f3c2ad062861f74d614d88c

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

@@ -25,21 +25,6 @@ use std::sync::atomic::AtomicBool;
 use std::sync::atomic::Ordering;
 use tracing::instrument;
 
-#[derive(Clone, Debug)]
-pub(crate) struct TurnSkillsContext {
-    pub(crate) snapshot: HostSkillsSnapshot,
-    pub(crate) implicit_invocation_seen_skills: Arc<Mutex<HashSet<String>>>,
-}
-
-impl TurnSkillsContext {
-    pub(crate) fn new(snapshot: HostSkillsSnapshot) -> Self {
-        Self {
-            snapshot,
-            implicit_invocation_seen_skills: Arc::new(Mutex::new(HashSet::new())),
-        }
-    }
-}
-
 pub(crate) type ShellSnapshotTask = Shared<BoxFuture<'static, Option<Arc<ShellSnapshotFile>>>>;
 
 #[derive(Clone)]
@@ -151,7 +136,6 @@ pub struct TurnContext {
     pub(crate) dynamic_tools: Vec<DynamicToolSpec>,
     pub(crate) turn_metadata_state: Arc<TurnMetadataState>,
     pub(crate) extension_data: Arc<codex_extension_api::ExtensionData>,
-    pub(crate) turn_skills: TurnSkillsContext,
     pub(crate) turn_timing_state: Arc<TurnTimingState>,
     pub(crate) terminal_error: Arc<Mutex<Option<ErrorEvent>>>,
     pub(crate) server_model_warning_emitted: AtomicBool,
@@ -164,6 +148,13 @@ enum TurnMultiAgentRuntime {
 }
 
 impl TurnContext {
+    pub(crate) fn skills_snapshot(&self) -> Arc<HostSkillsSnapshot> {
+        let Some(snapshot) = self.extension_data.get::<HostSkillsSnapshot>() else {
+            unreachable!("every turn has a host skills snapshot");
+        };
+        snapshot
+    }
+
     pub(crate) fn collaboration_mode(&self) -> CollaborationMode {
         CollaborationMode {
             mode: self.mode,
@@ -319,7 +310,6 @@ impl TurnContext {
             dynamic_tools: self.dynamic_tools.clone(),
             turn_metadata_state: self.turn_metadata_state.clone(),
             extension_data: Arc::clone(&self.extension_data),
-            turn_skills: self.turn_skills.clone(),
             turn_timing_state: Arc::clone(&self.turn_timing_state),
             terminal_error: Arc::clone(&self.terminal_error),
             server_model_warning_emitted: AtomicBool::new(
@@ -548,7 +538,7 @@ impl Session {
         ));
         let (current_date, timezone) = local_time_context();
         let extension_data = Arc::new(codex_extension_api::ExtensionData::new(sub_id.clone()));
-        extension_data.insert(skills_snapshot.clone());
+        extension_data.insert(skills_snapshot);
         TurnContext {
             sub_id,
             trace_id: current_span_trace_id(),
@@ -589,7 +579,6 @@ impl Session {
             dynamic_tools: session_configuration.dynamic_tools.clone(),
             turn_metadata_state,
             extension_data,
-            turn_skills: TurnSkillsContext::new(skills_snapshot),
             turn_timing_state: Arc::new(TurnTimingState::default()),
             terminal_error: Arc::new(Mutex::new(None)),
             server_model_warning_emitted: AtomicBool::new(false),