Record the multi-agent version in turn analytics (#51333)

## What changed

Carry `multi_agent_version` from the turn context through resolved configuration facts into turn analytics events.

## Testing

Extend the turn event serialization test to assert that `MultiAgentVersion::V2` is emitted as `"v2"` in `multi_agent_version`.

GitOrigin-RevId: f3e8c98588926d41a18c3db9aa229677e68cf5c1

codex-rs/analytics/src/events.rs

@@ -1101,6 +1101,7 @@ pub(crate) struct CodexTurnEventParams {
     pub(crate) approval_policy: String,
     pub(crate) approvals_reviewer: String,
     pub(crate) guardian_v2_enabled: bool,
+    pub(crate) multi_agent_version: codex_protocol::protocol::MultiAgentVersion,
     pub(crate) sandbox_network_access: bool,
     pub(crate) collaboration_mode: Option<&'static str>,
     pub(crate) personality: Option<String>,

codex-rs/analytics/src/facts.rs

@@ -207,6 +207,7 @@ pub struct TurnResolvedConfigFact {
     pub approval_policy: AskForApproval,
     pub approvals_reviewer: ApprovalsReviewer,
     pub guardian_v2_enabled: bool,
+    pub multi_agent_version: codex_protocol::protocol::MultiAgentVersion,
     pub sandbox_network_access: bool,
     pub collaboration_mode: ModeKind,
     pub personality: Option<Personality>,

codex-rs/analytics/src/reducer.rs

@@ -3654,6 +3654,7 @@ fn codex_turn_event_params(
         approval_policy,
         approvals_reviewer,
         guardian_v2_enabled,
+        multi_agent_version,
         sandbox_network_access,
         collaboration_mode,
         personality,
@@ -3704,6 +3705,7 @@ fn codex_turn_event_params(
         approval_policy: approval_policy.to_string(),
         approvals_reviewer: approvals_reviewer.to_string(),
         guardian_v2_enabled,
+        multi_agent_version,
         sandbox_network_access,
         collaboration_mode: Some(collaboration_mode_mode(collaboration_mode)),
         personality: personality_mode(personality),

codex-rs/analytics/src/tests/suite/turns/events_tests.rs

@@ -129,6 +129,7 @@ fn turn_event_serializes_expected_shape() {
             approval_policy: "on-request".to_string(),
             approvals_reviewer: "auto_review".to_string(),
             guardian_v2_enabled: true,
+            multi_agent_version: codex_protocol::protocol::MultiAgentVersion::V2,
             sandbox_network_access: true,
             collaboration_mode: Some("plan"),
             personality: Some("pragmatic".to_string()),
@@ -221,6 +222,7 @@ fn turn_event_serializes_expected_shape() {
                 "approval_policy": "on-request",
                 "approvals_reviewer": "auto_review",
                 "guardian_v2_enabled": true,
+                "multi_agent_version": "v2",
                 "sandbox_network_access": true,
                 "collaboration_mode": "plan",
                 "personality": "pragmatic",

codex-rs/analytics/src/tests/support.rs

@@ -360,6 +360,7 @@ pub(super) fn sample_turn_resolved_config(
         approval_policy: AskForApproval::OnRequest,
         approvals_reviewer: ApprovalsReviewer::AutoReview,
         guardian_v2_enabled: false,
+        multi_agent_version: codex_protocol::protocol::MultiAgentVersion::Disabled,
         sandbox_network_access: true,
         collaboration_mode: ModeKind::Plan,
         personality: None,

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

@@ -1298,6 +1298,7 @@ async fn track_turn_resolved_config_analytics(
                 .get::<codex_extension_api::GuardianV2Enabled>()
                 .is_some(),
             sandbox_network_access: turn_context.network_sandbox_policy().is_enabled(),
+            multi_agent_version: turn_context.multi_agent_version,
             collaboration_mode: turn_context.mode(),
             personality: turn_context.personality(),
             workspace_kind: turn_context.turn_metadata_state.workspace_kind(),