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/skills.rs

@@ -10,6 +10,8 @@ use codex_otel::sanitize_metric_tag_value;
 use codex_protocol::protocol::SkillScope;
 use codex_utils_absolute_path::AbsolutePathBuf;
 use codex_utils_plugins::PluginSkillRoot;
+use std::collections::HashSet;
+use tokio::sync::Mutex;
 
 pub use codex_core_skills::SkillError;
 pub use codex_core_skills::SkillLoadOutcome;
@@ -31,6 +33,9 @@ pub use codex_core_skills::system;
 pub use codex_skills::SkillMetadata;
 pub use codex_skills::SkillPolicy;
 
+#[derive(Debug, Default)]
+struct ImplicitSkillInvocations(Mutex<HashSet<String>>);
+
 pub(crate) fn skills_load_input_from_config(
     config: &Config,
     effective_skill_roots: Vec<PluginSkillRoot>,
@@ -50,7 +55,7 @@ pub(crate) async fn maybe_emit_implicit_skill_invocation(
     workdir: &AbsolutePathBuf,
 ) {
     let Some(candidate) = detect_implicit_skill_invocation_for_command(
-        turn_context.turn_skills.snapshot.outcome(),
+        turn_context.skills_snapshot().outcome(),
         command,
         workdir,
     ) else {
@@ -74,11 +79,10 @@ pub(crate) async fn maybe_emit_implicit_skill_invocation(
     let skill_name = invocation.skill_name.clone();
     let seen_key = format!("{skill_scope}:{skill_path}:{skill_name}");
     let inserted = {
-        let mut seen_skills = turn_context
-            .turn_skills
-            .implicit_invocation_seen_skills
-            .lock()
-            .await;
+        let skill_invocations = turn_context
+            .extension_data
+            .get_or_init(ImplicitSkillInvocations::default);
+        let mut seen_skills = skill_invocations.0.lock().await;
         seen_skills.insert(seen_key)
     };
     if !inserted {