Provider discovery

Trussium exposes bounded metadata for explicitly configured providers through GET /v1/providers. The endpoint reads the sealed ProviderRegistry snapshot and never executes providers or performs network probes.

Each entry contains the provider name, version, supported provider-neutral capability identities, and optional description. Credentials, URLs, models, implementations, health, availability, prompts, responses, and provider payloads are intentionally excluded.

The capabilities array is the provider capability report. It is an immutable, declaration-time view of the capability identities the adapter registers; an entry means the provider advertises that contract, not that an upstream service is currently reachable. Use GET /v1/providers/health for bounded informational health checks and GET /v1/capabilities/availability for runtime capability availability. Those probes remain separate from discovery and never alter provider registration.

Provider registration remains application-owned. Operators construct providers, register them before application startup, and the application seals the registry before serving traffic. Package scanning and configuration-driven imports remain out of scope.