[codex-core-plugins] Remote Plugin ID Persisted to File (#27669)

## This PR

Remote plugin analytics cannot rely only on the in-memory
installed-plugin snapshot because that snapshot is refreshed
asynchronously after startup. This PR persists the authoritative backend
identity alongside each cached remote plugin bundle so later consumers
can resolve it without a network request.

### Behavior

- Store Codex-owned remote installation metadata in an atomic
`.codex-remote-plugin-install.json` sidecar under the plugin cache root.
- Use a versioned, snake_case schema:

  ```json
  {
    "schema_version": 1,
    "remote_plugin_id": "plugins~Plugin_..."
  }
  ```

- Write the metadata during remote bundle installation.
- Backfill it when bundle sync finds an already-current cached bundle.
- Clear it when a generic/local install replaces the cache.
- Let existing uninstall and stale-cache removal delete it with the
plugin cache root.
- Reject unsupported schema versions rather than silently misreading
future formats.

This PR does not change analytics serialization or event behavior.

### Review surface

The implementation is limited to four `codex-core-plugins` files:

- `store.rs`: owns the versioned sidecar read/write/remove lifecycle.
- `remote_bundle.rs`: persists the backend ID after a remote bundle
install.
- `remote/remote_installed_plugin_sync.rs`: backfills metadata for an
already-current cached bundle.
- Tests cover the storage lifecycle and both remote write paths.

## Testing / Validation

### Automated

- `just test -p codex-core-plugins` (268 tests passed)
- `just fix -p codex-core-plugins` passes with one pre-existing
`large_enum_variant` warning in `manifest.rs`.
- Coverage verifies the exact filename and JSON schema, identity
replacement, local reinstall clearing, uninstall cleanup, remote bundle
installation, unsupported schema rejection, and installed-plugin sync
backfill.

### Live manual validation

Validated the production app-server RPC path with an isolated temporary
`CODEX_HOME` and the PR-built Codex binary. The app-server communicated
over stdio and did not bind a port.

Test plugin: `plugins~Plugin_b80dd84519148191a409cde181c9b3d6`
(`build-macos-apps@openai-curated-remote`).

1. Confirmed `plugin/read` initially reported the plugin uninstalled.
2. Installed it through `plugin/install` and confirmed version `0.1.4`
was cached.
3. Verified
`$CODEX_HOME/plugins/cache/openai-curated-remote/build-macos-apps/.codex-remote-plugin-install.json`
was created beside the `0.1.4/` bundle directory with mode `0600` and
the expected contents:

   ```json
   {
     "schema_version": 1,
"remote_plugin_id": "plugins~Plugin_b80dd84519148191a409cde181c9b3d6"
   }
   ```

4. Deleted only the sidecar, restarted the app-server, and confirmed
installed-plugin startup sync recreated it with the same contents.
5. Uninstalled through `plugin/uninstall`, confirmed `plugin/read`
returned `installed: false`, and verified the local plugin cache root
was removed.
6. Restored the account's original uninstalled state and removed the
isolated home and copied credentials.

## Split Overview

```text
main
├── #27093  Debug analytics capture                     merged
│   └── #27099  Non-mutating plugin smoke               merged
│       └── #27100  Remote install/uninstall smoke      merged
└── #27102  Plugin telemetry metadata refactor          merged
    └── #27669  Persist remote plugin identity           ← this PR

Next:
└── Final PR: add explicit local and remote IDs to plugin analytics
```

This PR is based directly on `main`; prerequisite
[#27102](https://github.com/openai/codex/pull/27102) has merged. The
original combined [#26281](https://github.com/openai/codex/pull/26281)
remains the aggregate reference until the final replacement PR is
published.

codex-rs/core-plugins/src/remote_bundle.rs

@@ -34,6 +34,7 @@ const TEST_ALLOW_LOOPBACK_HTTP_REMOTE_PLUGIN_BUNDLES_ENV: &str =
 pub struct ValidatedRemotePluginBundle {
     pub plugin_id: PluginId,
     pub plugin_version: String,
+    remote_plugin_id: String,
     app_manifest: Option<JsonValue>,
     bundle_download_url: String,
 }
@@ -190,6 +191,7 @@ pub fn validate_remote_plugin_bundle(
     Ok(ValidatedRemotePluginBundle {
         plugin_id,
         plugin_version,
+        remote_plugin_id: remote_plugin_id.to_string(),
         app_manifest,
         bundle_download_url,
     })
@@ -403,9 +405,12 @@ fn install_remote_plugin_bundle(
     })?;
 
     let store = PluginStore::try_new(codex_home)?;
-    store
+    let remote_plugin_id = bundle.remote_plugin_id;
+    let result = store
         .install_with_version(plugin_root, bundle.plugin_id, bundle.plugin_version)
-        .map_err(RemotePluginBundleInstallError::from)
+        .map_err(RemotePluginBundleInstallError::from)?;
+    store.write_remote_plugin_id(&result.plugin_id, &remote_plugin_id)?;
+    Ok(result)
 }
 
 fn extract_remote_plugin_bundle_to_path(
@@ -745,6 +750,43 @@ mod tests {
         );
     }
 
+    #[test]
+    fn install_persists_remote_plugin_install_metadata() {
+        let codex_home = tempdir().expect("tempdir");
+        let bundle = valid_remote_plugin_bundle();
+
+        let result = install_remote_plugin_bundle(
+            codex_home.path().to_path_buf(),
+            bundle,
+            tar_gz_bytes(&[(
+                ".codex-plugin/plugin.json",
+                br#"{"name":"linear","version":"1.2.3"}"#,
+                /*mode*/ 0o644,
+            )]),
+        )
+        .expect("install bundle");
+        let store = PluginStore::new(codex_home.path().to_path_buf());
+
+        assert_eq!(
+            store.remote_plugin_id(&result.plugin_id).unwrap(),
+            Some(REMOTE_PLUGIN_ID.to_string())
+        );
+        let metadata_path = store
+            .plugin_base_root(&result.plugin_id)
+            .join(".codex-remote-plugin-install.json");
+        assert_eq!(
+            serde_json::from_str::<serde_json::Value>(
+                &std::fs::read_to_string(metadata_path.as_path())
+                    .expect("read remote plugin install metadata")
+            )
+            .expect("parse remote plugin install metadata"),
+            serde_json::json!({
+                "schema_version": 1,
+                "remote_plugin_id": REMOTE_PLUGIN_ID,
+            })
+        );
+    }
+
     #[test]
     fn install_preserves_non_global_bundle_manifest_metadata() {
         let codex_home = tempdir().expect("tempdir");