Build tooling around the Pocket modality

Make a Pocket card something any product team can build, preview, deploy and test on their own without reading Kotlin, touching the Android repo, or redeploying between visual changes.

Done when a product engineer, from their own repo and a Firebase debug build, can:

1. Add a worker to a product and declare a card on it
2. Change how the card looks and see it on a device in under a minute, no deploy
3. Deploy the worker, and have a malformed card fail at deploy time rather than silently on device
4. Add the card with a deeplink and watch the live face redraw, with button presses reaching the worker

Background and reasoning: docs/pocket-card-developer-experience.md and docs/pocket-card-dev-loop.md
in polkadot-android-community.

polkadot-android-community

• Let the debug worker override carry a Pocket card (id, title, face URL beside the worker URL)
• On-device face preview: draw a face from a URL through the production decoder and renderer
• Browser-reachable loop for testers with no adb (today the fast loop needs a cable)

product-sdk

• A worker entry point — a blessed way to write the bundle the manifest points at
• A typed face builder producing RendererNode, so enum names and node shapes are checked at compile time
• validateFace(json) usable in a test and in CI, returning the same verdict the host reaches
• Handler registration for renderer.onRender on the PocketCard context, plus pocket.listSubscribe / pocket.removeCard wrappers
• A worked example, and a skill in the repo's Claude Code marketplace
• A guide: add a worker, declare a card, preview it, deploy it, add it, remove it

bulletin-deploy

• Validate pocket.cards in the worker manifest: ids screened as the core screens them, unique per worker, non-blank titles

humanity (first customer)

• Publish a worker on peopl.<tld> with includes.pocket: true and a card with id humanity — the pinned card hands over to it the moment that record exists

Start with docs/pocket-card-developer-experience.md and docs/pocket-card-dev-loop.md. Then map the unchecked work across polkadot-android-community, product-sdk, and bulletin-deploy, beginning with the worker entry point and face validation path. Done means the listed product workflow works from a product repository and Firebase debug build, including preview, deploy-time validation, deeplink rendering, and worker button handling.