Remove obsolete Guardian thread-context enables from tests (#51184)

## Why

Thread-owned Guardian context is always enabled, and `guardianv2.thread_context` is deprecated and ignored.

## What changed

Remove explicit `GuardianThreadContext` enables from retained-context and heartbeat tests. Parameterize the heartbeat skill-context test with optional feature lists so it covers the default behavior and `GuardianRootHandoffContext`, each with one or three heartbeats.

GitOrigin-RevId: 78e3159832bff08b79c7977d876d9acb587e9c71

codex-rs/core/tests/suite/guardian_heartbeat_authorization.rs

@@ -183,20 +183,23 @@ async fn heartbeat_keeps_user_restriction_after_status_questions(
     Ok(())
 }
 
-#[test_case::test_case(Feature::GuardianThreadContext, 1; "existing_projection_first")]
-#[test_case::test_case(Feature::GuardianThreadContext, 3; "existing_projection_repeated")]
-#[test_case::test_case(Feature::GuardianRootHandoffContext, 1; "handoff_filter_first")]
-#[test_case::test_case(Feature::GuardianRootHandoffContext, 3; "handoff_filter_repeated")]
+#[test_case::test_case(&[], 1; "existing_projection_first")]
+#[test_case::test_case(&[], 3; "existing_projection_repeated")]
+#[test_case::test_case(&[Feature::GuardianRootHandoffContext], 1; "handoff_filter_first")]
+#[test_case::test_case(&[Feature::GuardianRootHandoffContext], 3; "handoff_filter_repeated")]
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn heartbeat_root_projection_uses_latest_turn_skills(
-    feature: Feature,
+    enabled_features: &'static [Feature],
     heartbeat_count: usize,
 ) -> Result<()> {
     skip_if_no_network!(Ok(()));
     let server = start_mock_server().await;
     let test = test_codex()
         .with_config(move |config| {
-            for feature in [Feature::Collab, Feature::MultiAgentV2, feature] {
+            for feature in [Feature::Collab, Feature::MultiAgentV2]
+                .into_iter()
+                .chain(enabled_features.iter().copied())
+            {
                 config.features.enable(feature).expect("enable feature");
             }
         })

codex-rs/core/tests/suite/guardian_retained_context.rs

@@ -295,10 +295,6 @@ async fn streamed_question_precedes_reply_across_resume(
         .with_history_mode(ThreadHistoryMode::Paginated)
         .with_config(|config| {
             config.experimental_thread_store = ThreadStoreConfig::Local;
-            config
-                .features
-                .enable(Feature::GuardianThreadContext)
-                .expect("enable retained context");
         })
         .build_with_streaming_server(&server)
         .await?;

codex-rs/core/tests/suite/scenarios_guardian_agent_messages_tests.rs

@@ -1,7 +1,6 @@
 //! Guardian retains native encrypted parent replies across incremental reviews.
 
 use codex_core::config::Constrained;
-use codex_features::Feature;
 use codex_protocol::AgentPath;
 use codex_protocol::config_types::ApprovalsReviewer;
 use codex_protocol::models::PermissionProfile;
@@ -66,10 +65,6 @@ async fn encrypted_parent_reply_survives_incremental_guardian_reviews() -> anyho
         .with_model("gpt-5.5")
         .with_config(|config| {
             super::configure_scenario_catalog(config);
-            config
-                .features
-                .enable(Feature::GuardianThreadContext)
-                .unwrap();
             config.approvals_reviewer = ApprovalsReviewer::AutoReview;
             config.permissions.approval_policy = Constrained::allow_any(AskForApproval::OnRequest);
             config

codex-rs/core/tests/suite/scenarios_guardian_heartbeat.rs

@@ -58,10 +58,6 @@ async fn heartbeat_repetitions_keep_later_human_authorization() -> anyhow::Resul
                 .features
                 .disable(Feature::EnableRequestCompression)
                 .unwrap();
-            config
-                .features
-                .enable(Feature::GuardianThreadContext)
-                .unwrap();
             config.approvals_reviewer = ApprovalsReviewer::AutoReview;
             config.permissions.approval_policy = Constrained::allow_any(AskForApproval::OnRequest);
             config