feat: Add remote plugin fields to plugin API (#17277)

## Summary
Update the plugin API for the new remote plugin model.

The mental model is no longer “keep local plugin state in sync with
remote.” Instead, local and remote plugins are becoming separate
sources. Remote catalog entries can be shown directly from the remote
API before installation; after installation they are still downloaded
into the local cache for execution, but remote installed state will come
from the API and be held in memory rather than being read from config.

• ## API changes
- Remove `forceRemoteSync` from `plugin/list`, `plugin/install`, and
`plugin/uninstall`.
  - Remove `remoteSyncError` from `plugin/list`.
  - Add remote-capable metadata to `plugin/list` / `plugin/read`:
    - nullable `marketplaces[].path`
    - `source: { type: "remote", downloadUrl }`
    - URL asset fields alongside local path fields:
  `composerIconUrl`, `logoUrl`, `screenshotUrls`
  - Make `plugin/read` and `plugin/install` source-compatible:
    - `marketplacePath?: AbsolutePathBuf | null`
    - `remoteMarketplaceName?: string | null`
    - exactly one source is required at runtime

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

@@ -565,9 +565,7 @@ impl PluginsManager {
             self.restriction_product,
         )?;
         let plugin_id = resolved.plugin_id.as_key();
-        // This only forwards the backend mutation before the local install flow. We rely on
-        // `plugin/list(forceRemoteSync=true)` to sync local state rather than doing an extra
-        // reconcile pass here.
+        // This only forwards the backend mutation before the local install flow.
         codex_core_plugins::remote::enable_remote_plugin(
             &remote_plugin_service_config(config),
             auth,
@@ -655,11 +653,11 @@ impl PluginsManager {
         auth: Option<&CodexAuth>,
         plugin_id: String,
     ) -> Result<(), PluginUninstallError> {
+        // TODO: Remove this legacy remote-sync path once remote plugins have
+        // their own manager and installed-state API.
         let plugin_id = PluginId::parse(&plugin_id)?;
         let plugin_key = plugin_id.as_key();
-        // This only forwards the backend mutation before the local uninstall flow. We rely on
-        // `plugin/list(forceRemoteSync=true)` to sync local state rather than doing an extra
-        // reconcile pass here.
+        // This only forwards the backend mutation before the local uninstall flow.
         codex_core_plugins::remote::uninstall_remote_plugin(
             &remote_plugin_service_config(config),
             auth,