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-agent-form-state.ts

@@ -76,6 +76,7 @@ export interface UseAgentFormStateResult {
   refreshProviderModels: (provider?: AgentProvider) => void;
   refetchProviderModelsIfStale: () => void;
   setProviderAndModelFromUser: (provider: AgentProvider, modelId: string) => void;
+  clearProviderSelectionFromUser: () => void;
   workingDirIsEmpty: boolean;
   persistFormPreferences: () => Promise<void>;
 }
@@ -404,6 +405,10 @@ export function useAgentFormState(options: UseAgentFormStateOptions = {}): UseAg
     ],
   );
 
+  const clearProviderSelectionFromUser = useCallback(() => {
+    dispatch({ type: "CLEAR_PROVIDER_SELECTION_FROM_USER" });
+  }, []);
+
   const setModeFromUser = useCallback(
     (modeId: string) => {
       dispatch({ type: "SET_MODE_FROM_USER", modeId });
@@ -547,6 +552,7 @@ export function useAgentFormState(options: UseAgentFormStateOptions = {}): UseAg
       refreshProviderModels,
       refetchProviderModelsIfStale,
       setProviderAndModelFromUser,
+      clearProviderSelectionFromUser,
       workingDirIsEmpty,
       persistFormPreferences,
     }),
@@ -581,6 +587,7 @@ export function useAgentFormState(options: UseAgentFormStateOptions = {}): UseAg
       refreshProviderModels,
       refetchProviderModelsIfStale,
       setProviderAndModelFromUser,
+      clearProviderSelectionFromUser,
       workingDirIsEmpty,
       persistFormPreferences,
     ],