fix: optimistic archiving/closing and tab UX improvements

- Archive agents optimistically on close with rollback on error
- Close tabs immediately instead of waiting for RPC response
- Kill terminals in background with cache invalidation on failure
- Bulk close fires RPC in background, closes all tabs upfront
- Move new-tab button out of scroll area, rename to "New agent tab"
- Support invalidateQueries option in applyArchivedAgentCloseResults
- Fix workspace descriptor id/projectId types (string not number)

packages/app/src/hooks/use-sidebar-workspaces-list.ts

@@ -259,8 +259,8 @@ function getWorkspaceOrderScopeKey(serverId: string, projectKey: string): string
 }
 
 function toWorkspaceDescriptor(payload: {
-  id: number;
-  projectId: number;
+  id: string;
+  projectId: string;
   projectDisplayName: string;
   projectRootPath: string;
   workspaceDirectory: string;