[codex-analytics] add extensible feature thread sources (#27063)

## Why
- `ThreadSource` currently defines a closed set of core-owned values
- Product features also create threads for background or scheduled work
- Adding every product-specific value to the core enum would require
repeated `codex-rs` protocol changes
- Feature-backed values let product callers provide precise attribution
while preserving the existing core classifications

## What Changed
- Adds `ThreadSource::Feature(String)` for app-owned thread source
values
- Represents all app-server v2 thread sources as scalar strings, so a
feature source is supplied as `"automation"`
- Persists and emits the feature's plain string label, so `"automation"`
produces `thread_source="automation"` in analytics
- Keeps `user`, `subagent`, and `memory_consolidation` as explicit
core-owned values and regenerates the app-server schemas and TypeScript
bindings

## Verification
- `just write-app-server-schema`
- `cargo check --workspace`
- `just test -p codex-protocol
feature_thread_source_serializes_as_its_app_owned_label`
- `just test -p codex-app-server-protocol
thread_sources_round_trip_as_scalar_labels`
- `cargo test -p codex-analytics
thread_initialized_event_serializes_expected_shape`
- `just fmt`

codex-rs/analytics/src/analytics_client_tests.rs

@@ -1374,7 +1374,7 @@ fn thread_initialized_event_serializes_expected_shape() {
             },
             model: "gpt-5".to_string(),
             ephemeral: true,
-            thread_source: Some(ThreadSource::User),
+            thread_source: Some(ThreadSource::Feature("automation".to_string())),
             initialization_mode: ThreadInitializationMode::New,
             subagent_source: None,
             parent_thread_id: None,
@@ -1407,7 +1407,7 @@ fn thread_initialized_event_serializes_expected_shape() {
                 },
                 "model": "gpt-5",
                 "ephemeral": true,
-                "thread_source": "user",
+                "thread_source": "automation",
                 "initialization_mode": "new",
                 "subagent_source": null,
                 "parent_thread_id": null,

codex-rs/analytics/src/reducer.rs

@@ -1263,7 +1263,7 @@ impl AnalyticsReducer {
                     thread_metadata.session_id.clone(),
                     connection_state.app_server_client.clone(),
                     connection_state.runtime.clone(),
-                    thread_metadata.thread_source,
+                    thread_metadata.thread_source.clone(),
                     thread_metadata.subagent_source.clone(),
                     thread_metadata.parent_thread_id.clone(),
                 ),
@@ -1368,7 +1368,7 @@ impl AnalyticsReducer {
                 accepted_turn_id,
                 app_server_client: connection_state.app_server_client.clone(),
                 runtime: connection_state.runtime.clone(),
-                thread_source: thread_metadata.thread_source,
+                thread_source: thread_metadata.thread_source.clone(),
                 subagent_source: thread_metadata.subagent_source.clone(),
                 parent_thread_id: thread_metadata.parent_thread_id.clone(),
                 num_input_images: pending_request.num_input_images,
@@ -1411,7 +1411,7 @@ impl AnalyticsReducer {
                 review_id: pending_review.review_id,
                 app_server_client: connection_state.app_server_client.clone(),
                 runtime: connection_state.runtime.clone(),
-                thread_source: thread_metadata.thread_source,
+                thread_source: thread_metadata.thread_source.clone(),
                 subagent_source: thread_metadata.subagent_source.clone(),
                 parent_thread_id: thread_metadata.parent_thread_id.clone(),
                 subject_kind: pending_review.subject_kind,
@@ -1979,7 +1979,7 @@ fn tool_item_base(
         item_id,
         app_server_client: context.connection_state.app_server_client.clone(),
         runtime: context.connection_state.runtime.clone(),
-        thread_source: thread_metadata.thread_source,
+        thread_source: thread_metadata.thread_source.clone(),
         subagent_source: thread_metadata.subagent_source.clone(),
         parent_thread_id: thread_metadata.parent_thread_id.clone(),
         tool_name,
@@ -2459,7 +2459,7 @@ fn codex_turn_event_params(
         runtime,
         submission_type,
         ephemeral,
-        thread_source: thread_metadata.thread_source,
+        thread_source: thread_metadata.thread_source.clone(),
         initialization_mode: thread_metadata.initialization_mode,
         subagent_source: thread_metadata.subagent_source.clone(),
         parent_thread_id: thread_metadata.parent_thread_id.clone(),