feat(app/e2e): introduce withWorkspace fixture and DSL helpers (#717)

Adds a `withWorkspace` Playwright fixture plus composable helpers
(permissions, sidebar, composer, agent-stream, settings) so specs read
as user-level intent. Migrates workspace-lifecycle and settings-host-page
to the new DSL as proof.

packages/app/e2e/codex-plan-approval.spec.ts

@@ -1,6 +1,6 @@
 import { expect, test } from "./fixtures";
 import { buildHostWorkspaceRoute } from "@/utils/host-routes";
-import { allowPermission, waitForPermissionPrompt } from "./helpers/app";
+import { allowPermission, waitForPermissionPrompt } from "./helpers/permissions";
 import { connectTerminalClient } from "./helpers/terminal-perf";
 import { createTempGitRepo } from "./helpers/workspace";