Add async RegistryClient implementing the Package Registry Standard
v1.0.0 HTTP API endpoints (§8) using httpx.AsyncClient.
- GET /packages/{id} — retrieve package content by PackageId
- GET /{type}/{ns}/{name}?version= — resolve references with
version alias resolution (latest, vx, vX.Y.x, vX.x per §4.2)
- GET /browse — discover published packages with type/namespace filters
- GET /.well-known/cleverthis-packages — registry metadata discovery
- Maps all 8 standard error types (§13.2) to typed exceptions
- Supports anonymous reads (§9.1) and optional API key auth (§9.2)
- Async context manager support (__aenter__/__aexit__)
- 32 Behave BDD scenarios, 7 Robot Framework integration tests,
ASV benchmarks, 100% registry module coverage
ISSUES CLOSED: #24
CoreRasurae