Add a feature

A new feature usually touches every layer, in this order. Each step names the skill or file with the details. The posts feature is the reference for each step: open the one file a step names, not the whole folder.

1. Schema in src/server/db/schema/, then pnpm db:generate --name <slug> and pnpm db:migrate (skill database-change). A table of user content takes the shared columns of schema/columns.ts (uuidv7Id, authorId, createdAt, updatedAt, trimmedTextCheck) and, if it is listed, a keyset index ending in (created_at, id), as post has.
2. Contract in src/contract/: schemas, endpoints, tagged errors. Constants the UI also needs (limits, lengths) go in src/contract/limits.ts, which stays free of Effect (skill api-change). An input schema a form also validates goes in a module without HttpApi code (src/contract/post-input.ts), so the browser loads Schema only. A list endpoint takes query: PageQuery and answers pageOf(Item) (src/contract/pages.ts).
3. Repository (for example src/server/posts/repo.ts) and handler in src/server/api/handlers.ts, added to ApiHandlers there. Each statement goes through query (src/server/db/query.ts, with DbError and isUuid); a list reads a page with keyset(table) and toPage, and its handler turns the query into a request with pageRequest (src/server/db/keyset.ts). A write of several statements runs in Database.transaction(effect) (src/server/db/client.ts, proven in tests/db/transaction.test.ts). Provide the repository's Layer in src/server/api/web-handler.ts and an in-memory one in apiLayer (tests/api/harness.ts), built like tests/api/posts-repo.ts on memoryPage and memoryClock (tests/api/memory-keyset.ts). Name it src/server/<feature>/repo.ts: Oxlint keeps drivers and singletons out of that path.
4. pnpm codegen.
5. Errors: map every new error tag to a message in src/lib/api-error.ts. pnpm typecheck fails until describeApiError handles it.
6. UI in src/features/<name>/ (see "Where code goes" in AGENTS.md) and routes in src/routes/ (skill add-page for a new page). Reuse the shared list pieces src/features/AGENTS.md names instead of copying the posts ones: pnpm check fails on any duplicated block. A component takes the signed-in user from its route's context (Route.useRouteContext()), not useSessionUser: session.functions.ts has no component-test stub, and importing it breaks the tests' browser bundle. An account action follows the auth-change skill instead.
7. Tests, cheapest layer first, each with its folder's AGENTS.md: handler branches in tests/api/, UI states in tests/component/, query budgets in tests/db/, then tests/integration/ and tests/e2e/ (each new page or UI state gets an entry in STATES in tests/e2e/a11y.spec.ts; a section added to an existing page needs no edit to other states' keyboard rows or landmark snapshots).

Done when

pnpm check, pnpm check:drift and pnpm build && pnpm verify:app pass, and every generated file is committed with its source. Run pnpm check after each layer. At the end, run pnpm build && pnpm verify:app through the verifier subagent; while fixing, rerun only the layer that failed (its summary names the command), then run the whole verify:app once more. The feature is done only when that last full run passed: contract coverage runs only there. Wait for the verifier's report each time (call it in the foreground, or wait for a background run to finish) and act on it before you report the feature: ending while it still runs hands over unverified work. Every status the contract declares needs a test that provokes it (the api layer counts): a 400 for an operation with a body or query, a 429 for a rate-limited write.