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/src/hooks/use-schedules.ts

@@ -0,0 +1,60 @@
+import { useMemo, useSyncExternalStore } from "react";
+import { useQuery } from "@tanstack/react-query";
+import { getHostRuntimeStore, useHosts } from "@/runtime/host-runtime";
+import {
+  fetchAggregatedSchedules,
+  type ScheduleHostInput,
+  type ScheduleHostSection,
+} from "@/schedules/aggregated-schedules";
+
+export type { ScheduleHostSection } from "@/schedules/aggregated-schedules";
+
+export const schedulesQueryBaseKey = ["schedules"] as const;
+
+export function schedulesQueryKey(hosts: readonly ScheduleHostInput[]) {
+  return [...schedulesQueryBaseKey, hosts.map((host) => host.serverId).join("|")] as const;
+}
+
+export interface UseSchedulesResult {
+  sections: ScheduleHostSection[];
+  isLoading: boolean;
+  isError: boolean;
+  error: Error | null;
+  refetch: () => void;
+  isRefetching: boolean;
+}
+
+export function useSchedules(): UseSchedulesResult {
+  const hosts = useHosts();
+  const runtime = getHostRuntimeStore();
+  const runtimeVersion = useSyncExternalStore(
+    (onStoreChange) => runtime.subscribeAll(onStoreChange),
+    () => runtime.getVersion(),
+    () => runtime.getVersion(),
+  );
+  const hostInputs = useMemo<ScheduleHostInput[]>(
+    () =>
+      hosts.map((host) => ({
+        serverId: host.serverId,
+        serverName: host.label,
+      })),
+    [hosts],
+  );
+
+  const query = useQuery({
+    queryKey: [...schedulesQueryKey(hostInputs), runtimeVersion] as const,
+    queryFn: () => fetchAggregatedSchedules({ hosts: hostInputs, runtime }),
+    staleTime: 5_000,
+  });
+
+  return {
+    sections: query.data?.sections ?? [],
+    isLoading: query.isLoading,
+    isError: query.isError,
+    error: query.error,
+    refetch: () => {
+      void query.refetch();
+    },
+    isRefetching: query.isRefetching,
+  };
+}