Extract dashboard EmptyState component (#61)

* review: harden readonly git checks and lint verification

* test: satisfy readonly reviewer sandbox typing

* test: fix readonly reviewer sandbox assertions

* test: remove impossible readonly sandbox guards

* test: relax readonly sandbox assertions

* test: cast readonly sandbox expectation shape

* test: cast readonly sandbox expectation through unknown

* Phase 0 — STEP_DONE/TASK_DONE split + owner-follow-up integration smoke

* Add STEP_DONE guards, verdict storage, and stale delivery suppression

* style: format paired stepdone telemetry files

* Route STEP_DONE through reviewer

* Add structured Discord attachments

* style: format structured attachment test

* Fix room thread bot output parity

* Remove duplicate work item attachment migration from owner branch

* Remove legacy dashboard rooms renderer

* Extract dashboard parsed body renderer

* Extract dashboard redaction helpers

* Extract dashboard RoomCardV2 component

* Include RoomCardV2 test in vitest suite

* Extract dashboard RoomBoardV2 component

* Extract dashboard EmptyState component

apps/dashboard/src/EmptyState.tsx

@@ -0,0 +1,5 @@
+import type { ReactNode } from 'react';
+
+export function EmptyState({ children }: { children: ReactNode }) {
+  return <div className="empty-state">{children}</div>;
+}