Add a Schedules screen to manage recurring agents (#1246)

* feat: add Schedules screen to manage scheduled agents

Adds a Schedules section in the sidebar header (below Sessions) for viewing
and managing new-agent schedules: recurring jobs that spawn an agent on a
cron or interval cadence.

- Borderless table showing provider icon, model, cadence, next run, and
  status, with row actions to edit, pause/resume, run now, and delete.
- Create/edit sheet that reuses the agent provider/model/mode/working-
  directory pickers, plus an interval/cron cadence editor with presets,
  validation, and a UTC preview.
- Responsive: hover-revealed row actions on desktop, an always-visible
  action menu on mobile.
- Data layer over the existing schedule RPCs (list/create/update/pause/
  resume/delete/run-once) with optimistic pause, resume, and delete.

Scope is limited to new-agent schedules for now.

* Make the schedule form controls visually consistent

Merge the provider and model pickers into the single nested selector the
draft screen uses, render it as a full-width field, mute the placeholder,
proportion the cadence segmented controls, unify the cron preset chips,
and route the sheet scroll through the themed scrollbar.

* Address schedules review feedback

* Translate schedule hook client fallback errors

* Make schedules global and project scoped

* Stabilize project settings transport E2E

* Reset schedule model on cross-host project change

* Reject malformed cron step expressions

* Tighten schedules project query freshness

* refactor(schedules): clean up review feedback

* test(schedules): extract fake host setup

* refactor(schedules): share cron expression parsing

Use one structural cron parser for app previews and daemon cadence validation so the accepted grammar cannot drift between surfaces.

Remove the unused host-scoped schedules redirect while keeping the global schedules route.

packages/app/e2e/projects-settings.spec.ts

@@ -282,9 +282,9 @@ test.describe("Projects settings — error UX", () => {
     page,
     editableProject,
   }) => {
-    // Drop the WS connection the moment a read_project_config_request is sent.
-    // Subsequent connections are proxied transparently so Reload can succeed.
-    await installReadTransportFailure(page);
+    // Reject read_project_config_request calls until the user clicks Reload.
+    // This keeps automatic reconnect refetches from racing past the callout.
+    const transportFailure = await installReadTransportFailure(page);
 
     await openProjects(page);
     await navigateToProjectSettings(page, editableProject.name);
@@ -292,7 +292,8 @@ test.describe("Projects settings — error UX", () => {
     await expectProjectSettingsError(page, "transport");
     await expectProjectSettingsFormHidden(page);
 
-    // The client reconnects after a ~1.5 s backoff; retry Reload until refetch succeeds.
+    // Retry Reload until the refetch wins any in-flight error-state rendering.
+    transportFailure.allowRecovery();
     await expect(async () => {
       await clickReloadProjectSettings(page);
       await expectNoProjectSettingsError(page, "transport", 3_000);