fix: invalidate model metadata cache after OpenCode restart (#1065)

After OpenCode restarts (via 'Reload Opencode' or server reconnection),
the UI's cached model metadata (context windows, pricing, etc.) was
never refreshed — the cache was fetched once at boot and reused forever.
This meant new/updated models from providers were invisible until a full
page reload.

Add invalidateModelMetadataCache action to useConfigStore that clears
the metadata cache and resets the in-flight tracker. Call it from
performConfigRefresh before re-loading providers.

packages/ui/src/stores/useAgentsStore.ts

@@ -612,6 +612,10 @@ async function performConfigRefresh(options: {
       useConfigStore.setState({ directoryScoped: {} });
     }
 
+    if (refreshProviders) {
+      useConfigStore.getState().invalidateModelMetadataCache();
+    }
+
     const sdkRefreshTasks: Promise<void>[] = [];
     for (const directory of directoriesToRefresh) {
       if (refreshProviders) {