Populate workspace kind on Codex turn events (#25135)

## Summary
- carry `workspace_kind` from Responses API client metadata into the
turn resolved analytics fact
- serialize the optional value on `codex_turn_event`
- cover both the turn metadata source and turn event serialization

The `workspace_kind` tells us whether a thread had a project attached vs
projectless. this is an indicator for who is adopting Codex for
knowledge work outside of coding

## Testing
- `env UV_CACHE_DIR=/private/tmp/uv-cache
/private/tmp/cargo-tools/bin/just fmt`
- `env PATH=/private/tmp/cargo-tools/bin:$PATH
CARGO_HOME=/private/tmp/cargo-home UV_CACHE_DIR=/private/tmp/uv-cache
/private/tmp/cargo-tools/bin/just test -p codex-analytics`
- `env PATH=/private/tmp/cargo-tools/bin:$PATH
CARGO_HOME=/private/tmp/cargo-home UV_CACHE_DIR=/private/tmp/uv-cache
/private/tmp/cargo-tools/bin/just test -p codex-core turn_metadata`

Paired with openai/openai#970661, which keeps forwarding the same
metadata key through Responses API headers.

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

@@ -640,6 +640,7 @@ async fn track_turn_resolved_config_analytics(
             sandbox_network_access: turn_context.network_sandbox_policy().is_enabled(),
             collaboration_mode: turn_context.collaboration_mode.mode,
             personality: turn_context.personality,
+            workspace_kind: turn_context.turn_metadata_state.workspace_kind(),
             is_first_turn,
         });
 }

codex-rs/core/src/turn_metadata.rs

@@ -33,6 +33,7 @@ const MODEL_KEY: &str = "model";
 const REASONING_EFFORT_KEY: &str = "reasoning_effort";
 const TURN_STARTED_AT_UNIX_MS_KEY: &str = "turn_started_at_unix_ms";
 const USER_INPUT_REQUESTED_DURING_TURN_KEY: &str = "user_input_requested_during_turn";
+const WORKSPACE_KIND_KEY: &str = "workspace_kind";
 const REQUEST_KIND_KEY: &str = "request_kind";
 const COMPACTION_KEY: &str = "compaction";
 const WINDOW_ID_KEY: &str = "window_id";
@@ -443,6 +444,14 @@ impl TurnMetadataState {
             Some(responsesapi_client_metadata);
     }
 
+    pub(crate) fn workspace_kind(&self) -> Option<String> {
+        self.responsesapi_client_metadata
+            .read()
+            .unwrap_or_else(std::sync::PoisonError::into_inner)
+            .as_ref()
+            .and_then(|metadata| metadata.get(WORKSPACE_KIND_KEY).cloned())
+    }
+
     pub(crate) fn set_turn_started_at_unix_ms(&self, turn_started_at_unix_ms: i64) {
         *self
             .turn_started_at_unix_ms

codex-rs/core/src/turn_metadata_tests.rs

@@ -546,6 +546,7 @@ fn turn_metadata_state_merges_client_metadata_without_replacing_reserved_fields(
     state.set_responsesapi_client_metadata(HashMap::from([
         ("fiber_run_id".to_string(), "fiber-123".to_string()),
         ("origin".to_string(), "東京".to_string()),
+        ("workspace_kind".to_string(), "projectless".to_string()),
         ("model".to_string(), "client-supplied".to_string()),
         (
             "reasoning_effort".to_string(),
@@ -580,6 +581,7 @@ fn turn_metadata_state_merges_client_metadata_without_replacing_reserved_fields(
 
     assert_eq!(json["fiber_run_id"].as_str(), Some("fiber-123"));
     assert_eq!(json["origin"].as_str(), Some("東京"));
+    assert_eq!(json["workspace_kind"].as_str(), Some("projectless"));
     assert_eq!(json["model"].as_str(), Some("client-supplied"));
     assert_eq!(json["reasoning_effort"].as_str(), Some("client-supplied"));
     assert_eq!(json["session_id"].as_str(), Some("session-a"));
@@ -619,6 +621,7 @@ fn turn_metadata_state_merges_client_metadata_without_replacing_reserved_fields(
     assert_eq!(meta["model"].as_str(), Some("gpt-5.4"));
     assert_eq!(meta["reasoning_effort"].as_str(), Some("high"));
     assert!(meta.get(WINDOW_ID_KEY).is_none());
+    assert_eq!(state.workspace_kind().as_deref(), Some("projectless"));
 }
 
 #[test]