Resolve per-thread multi-agent runtime (#25722)

Stack split from #25708. Original PR intentionally left open. This third
PR resolves the effective per-thread multi-agent runtime from persisted
metadata, inherited runtime, and current model selection.

codex-rs/core/src/tasks/mod.rs

@@ -44,6 +44,7 @@ use codex_otel::TURN_TOKEN_USAGE_METRIC;
 use codex_otel::TURN_TOOL_CALL_METRIC;
 use codex_protocol::models::ResponseItem;
 use codex_protocol::protocol::EventMsg;
+use codex_protocol::protocol::MultiAgentVersion;
 use codex_protocol::protocol::TokenUsage;
 use codex_protocol::protocol::TurnAbortReason;
 use codex_protocol::protocol::TurnAbortedEvent;
@@ -70,11 +71,14 @@ pub(crate) enum InterruptedTurnHistoryMarker {
 }
 
 impl InterruptedTurnHistoryMarker {
-    pub(crate) fn from_config(config: &Config) -> Self {
+    pub(crate) fn from_config_and_version(
+        config: &Config,
+        multi_agent_version: MultiAgentVersion,
+    ) -> Self {
         if !config.agent_interrupt_message_enabled {
             return Self::Disabled;
         }
-        if config.features.enabled(Feature::MultiAgentV2) {
+        if multi_agent_version == MultiAgentVersion::V2 {
             Self::Developer
         } else {
             Self::ContextualUser
@@ -841,7 +845,10 @@ impl Session {
 
         if reason == TurnAbortReason::Interrupted
             && let Some(marker) = interrupted_turn_history_marker(
-                InterruptedTurnHistoryMarker::from_config(task.turn_context.config.as_ref()),
+                InterruptedTurnHistoryMarker::from_config_and_version(
+                    task.turn_context.config.as_ref(),
+                    task.turn_context.multi_agent_version,
+                ),
             )
         {
             self.record_conversation_items(