Implement quick-add registry (task 21)

- Add url field to QuickAddAction; make action optional
- Add getQuickAdds() + SerializedQuickAddItem to registry so quick-add
  data can cross the server→client RSC boundary without serializing fns
- Update calendar/lists/notes manifests with navigation URLs
- QuickAddProvider wraps root layout: holds sheet/palette open state and
  global cmd/ctrl+k shortcut
- QuickAddSheet: bottom drawer on mobile, right-side popover on desktop,
  actions grouped by module
- CommandPalette: cmdk-powered modal with fuzzy filter and full keyboard
  nav (arrows + enter + esc)
- QuickAddFab: client button replacing the plain + stub in the dashboard
- Add .claude/** to ESLint ignores to prevent stale worktree artifacts
  from failing lint

All 4 E2E specs pass; typecheck, lint, and build clean.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/modules/_core/registry.ts

@@ -1,4 +1,4 @@
-import type { ModuleManifest, EntityTypeRegistration, DashboardWidget } from "./module";
+import type { ModuleManifest, EntityTypeRegistration, DashboardWidget, QuickAddAction } from "./module";
 
 const modules = new Map<string, ModuleManifest>();
 const entityTypes = new Map<string, EntityTypeRegistration>();
@@ -29,3 +29,28 @@ export function getEntityType(type: string): EntityTypeRegistration | undefined
 export function getWidget(id: string): DashboardWidget | undefined {
   return widgets.get(id);
 }
+
+export type QuickAddItem = QuickAddAction & { moduleId: string; moduleName: string };
+
+/** Serializable subset safe to pass from server components to client components. */
+export type SerializedQuickAddItem = {
+  id: string;
+  label: string;
+  icon?: string;
+  url: string;
+  moduleId: string;
+  moduleName: string;
+};
+
+export function getQuickAdds(): SerializedQuickAddItem[] {
+  return [...modules.values()].flatMap((manifest) =>
+    (manifest.quickAdds ?? []).map(({ id, label, icon, url }) => ({
+      id,
+      label,
+      icon,
+      url,
+      moduleId: manifest.id,
+      moduleName: manifest.name,
+    })),
+  );
+}