Cloudflare Chat Persistence

The deliverable is one file in the Worker — src/lib/chat-persistence.ts — exporting a factory that builds a ChatPersistence from the request's D1 binding, plus (when the app needs coordination) a Durable Object lock store. Tables go into the app's existing migrations/ directory and are applied with wrangler d1 migrations apply.

Do not create a package or a migration runner. Wrangler already tracks applied migrations; a second bookkeeping table only creates drift.

Read the Store Reference (docs/persistence/store-reference.md) for the store contracts, and ai-persistence/stores for the shape rules. This skill covers only the Cloudflare-specific parts.

1. Read the app before writing anything