feat(docs): publish Shadcn registry primitives (#48)

## Summary

Publish model-free DNS presentation components through the DomainKit
Shadcn registry while keeping lifecycle behavior in the installed Effect
Atom package.

## Usage

```sh
npx shadcn@latest add https://domain-kit.dev/r/dns-table.json
npx shadcn@latest add https://domain-kit.dev/r/dns-operation.json
```

## Boundary

| Channel | Owns | Does not own |
| --- | --- | --- |
| Shadcn registry | DNS tables, operations, statuses, provider marks,
copy controls, async states | Effect, Atom, transports, provider clients
|
| `@domainkit/react` | Connection, OAuth, provisioning, verification,
cleanup, shared lifecycle state | Host credentials in the browser |

The registry check parses generated TSX imports, installs all six items
into a disposable React 19/Vite consumer, then typechecks and builds it.

## Validation

- `bun run --cwd apps/docs registry:check`
- `bun run release:check`
- `bun run docs:build`
- `bun run docs:audit` — 0 errors, 0 warnings