void-offline-first-mutation

What problem does it solve? User-triggered writes in a PWA fail or silently lose data when the device is offline, on flaky wifi, or when the browser crashes mid-submission. This Skill provides a capture-queue + sync pattern so mutations are persisted locally, applied optimistically, and reconciled with the server when connectivity returns. ## Core Features & Use Cases - Durable capture-queue: Persists each mutation intent to IndexedDB before the UI confirms, so a browser crash never loses user input. - Idempotent sync engine: Each intent carries a client-generated UUID idempotency key, with status transitions (pending, syncing, committed, failed), exponential backoff from 2s to 4h, and a dead-letter UI for failed intents. - Server-side idempotency: Shows the inbox pattern for Server Actions that honor idempotency keys, plus server-wins conflict resolution. - Use Case: A field technician on mobile submits a form in a subway tunnel; the note appears instantly in the list via optimistic update, the intent is queued in IndexedDB, and it syncs automatically when the device comes back online. ## Quick Start Ask the agent to implement an offline-first mutation for a user-triggered write such as creating a note, using the capture-queue and sync pattern with an idempotency key.