Track remote plugin IDs in skill invocation analytics (#35262)

## What changed

- Add `remote_plugin_id` to skill invocation facts and analytics event parameters.
- Propagate the ID for both explicit and implicit plugin skill invocations.

## Testing

- Cover explicit and implicit remote plugin skill invocations with analytics integration tests.

GitOrigin-RevId: 3e1d25b5ff88dcff9c2b6c9fe44bca97e8778221

codex-rs/analytics/src/analytics_client_tests.rs

@@ -3587,6 +3587,7 @@ async fn reducer_ingests_skill_invoked_fact() {
                     skill_scope: codex_protocol::protocol::SkillScope::User,
                     skill_path,
                     plugin_id: None,
+                    remote_plugin_id: None,
                     invocation_type: InvocationType::Explicit,
                 }],
             })),
@@ -3605,6 +3606,7 @@ async fn reducer_ingests_skill_invoked_fact() {
                 "product_client_id": TEST_PRODUCT_CLIENT_ID,
                 "skill_scope": "user",
                 "plugin_id": null,
+                "remote_plugin_id": null,
                 "repo_url": null,
                 "thread_id": "thread-1",
                 "turn_id": "turn-1",
@@ -3616,7 +3618,7 @@ async fn reducer_ingests_skill_invoked_fact() {
 }
 
 #[tokio::test]
-async fn reducer_includes_plugin_id_for_plugin_skill_invocations() {
+async fn reducer_includes_plugin_ids_for_plugin_skill_invocations() {
     let mut reducer = AnalyticsReducer::default();
     let mut events = Vec::new();
     let tracking = test_tracking_context("thread-1", "turn-1");
@@ -3632,6 +3634,7 @@ async fn reducer_includes_plugin_id_for_plugin_skill_invocations() {
                     skill_scope: codex_protocol::protocol::SkillScope::User,
                     skill_path,
                     plugin_id: Some("sample@test".to_string()),
+                    remote_plugin_id: Some("plugins~Plugin_sample".to_string()),
                     invocation_type: InvocationType::Explicit,
                 }],
             })),
@@ -3641,8 +3644,11 @@ async fn reducer_includes_plugin_id_for_plugin_skill_invocations() {
 
     let payload = serde_json::to_value(&events).expect("serialize events");
     assert_eq!(
-        payload[0]["event_params"]["plugin_id"],
-        json!("sample@test")
+        (
+            &payload[0]["event_params"]["plugin_id"],
+            &payload[0]["event_params"]["remote_plugin_id"],
+        ),
+        (&json!("sample@test"), &json!("plugins~Plugin_sample"))
     );
 }