feat(queues): add persistent queue prototype

[sampolahtinen]

Introduces the first persistent queue walking skeleton for Composer. It provides a typed queue definition and producer/consumer API, durable Postgres storage, and an independent Compute dispatcher that pushes work to application services.

Changes

• Queue module: Adds defineQueues, queueProducer, queueConsumer, serveQueues, queues, and queueDispatcher under @prisma/composer-prisma-cloud/queues.
• Durable delivery: Stores messages, queue configuration, availability times, attempts, and leases in Postgres. Enqueue is idempotent, claims use FOR UPDATE SKIP LOCKED, and delivery is at least once.
• Retry policy: Adds per-queue fixedBackoff configuration, persisted delayed retries, maximum-attempt enforcement, and terminal failed messages.
• Deployable example: Adds examples/queues, where one Compute service hosts the UI, producer, and consumer while a separate dispatcher delivers messages. The fail-once control demonstrates a real failed first attempt and successful retry with the same message ID.
• Documentation and architecture: Adds the queue design specification, public-package exports, architecture classifications, authoring guidance, and prototype operational findings.

Why

Queues remain a Prisma Cloud module composed from existing Postgres and Compute primitives instead of becoming a Composer core primitive. Keeping the durable queue service separate from the dispatcher avoids a dependency cycle, permits consumers to enqueue follow-up work, and lets delivery continue without producer traffic.

Prototype boundaries

This is intentionally a draft walking skeleton. Batches, several competing consumer services, exponential retry, replay, pause and resume, and operational APIs are not implemented yet.

The deployment prototype also exposed two Composer lifecycle issues documented in .agents/diary/queues-prototype.md: artifact and binding updates can become active in the wrong order, and promoting a new continuously running Compute revision does not retire previous revisions. Only one dispatcher revision should run until deployment retirement or revision fencing is implemented.

Verification

• pnpm format
• pnpm typecheck — 78 tasks passed
• pnpm lint
• pnpm lint:casts
• pnpm lint:deps
• pnpm check:publish-deps
• pnpm --filter @internal/queues test — 10 tests passed, including real Postgres integration tests
• Deployed demo: three consecutive fail-once messages retried successfully with stable IDs after 5.1–5.3 seconds

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commit: 4499ebb