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/helpers/agent-stream.ts

@@ -0,0 +1,17 @@
+import { expect, type Page } from "@playwright/test";
+
+export async function awaitAssistantMessage(page: Page, hasText?: string | RegExp): Promise<void> {
+  const messages = page.getByTestId("assistant-message");
+  const target = hasText === undefined ? messages.first() : messages.filter({ hasText }).first();
+  await expect(target).toBeVisible({ timeout: 30_000 });
+}
+
+export async function awaitToolCall(page: Page, toolName: string | RegExp): Promise<void> {
+  await expect(
+    page.getByTestId("tool-call-badge").filter({ hasText: toolName }).first(),
+  ).toBeVisible({ timeout: 30_000 });
+}
+
+export async function expectAgentIdle(page: Page, timeout = 30_000): Promise<void> {
+  await expect(page.getByRole("button", { name: /stop|cancel/i })).toHaveCount(0, { timeout });
+}