Add pinnable new-tab targets to the tab row and sidebar

Any new-tab target (new agent, terminal, browser, or a terminal profile)
can be pinned as a quick-launch button. Pins are global client app state
(persisted), not daemon config, so the same set shows on every workspace;
profile pins resolve per host and are dropped where that profile is absent.

The sidebar mirror launches via a navigate-then-launch intent store rather
than calling the create handlers directly: terminal creation only works in
the mounted/focused workspace, so the sidebar requests the launch and the
workspace screen consumes it on focus.

packages/app/e2e/helpers/workspace-tabs.ts

@@ -93,6 +93,15 @@ export async function expectFirstTerminalTabContains(page: Page, text: string):
   );
 }
 
+export async function expectTerminalTabOpen(
+  page: Page,
+  options?: { timeout?: number },
+): Promise<void> {
+  await expect(
+    page.locator('[data-testid^="workspace-tab-terminal_"]').filter({ visible: true }).first(),
+  ).toBeVisible({ timeout: options?.timeout ?? 30_000 });
+}
+
 export async function sampleWorkspaceTabIds(
   page: Page,
   options: { durationMs?: number; intervalMs?: number } = {},