enhancement(registry): tighten adapter types, comments, and lifecycle coverage

Context

Consolidated non-blocking clarity and coverage follow-ups from the final review of PR #779.

Comment and documentation corrections

• Distinguish MCP _meta storage from SKILL x-abca-runtime frontmatter in the adapter header.
• Correct the claim that duplicate YAML keys are parser errors under js-yaml with { json: true }; the emitter prevents key injection by quoting/escaping caller-controlled values.
• Include SKILL in the resolve path commentary.
• Clarify that waitPastCreating waits only until the record leaves CREATING, not until a terminal lifecycle state.
• Clarify that autoApprove gates only the final approval call; create and submit always occur.

Type cleanup

• Evaluate a discriminated representation linking registry kind to its payload variant instead of a broad kind: string shape.
• Simplify DeleteAttempt to the states its consumers need, or document why all current states are valuable.

Keep any public RegistryClient port change separately reviewable and compatible with the architecture boundary.

Coverage gap

Add a delete-lifecycle test proving isComplete rethrows a non-retryable, non-404 GetRegistry failure rather than treating it as absent or retryable.

References

• PR #779
• cdk/src/handlers/shared/registry/agent-registry-client.ts
• cdk/src/handlers/registry-provisioning/index.ts

Lee cdk/src/handlers/shared/registry/agent-registry-client.ts y cdk/src/handlers/registry-provisioning/index.ts, usando PR #779 como contexto. Traza el ciclo de vida de eliminación y el límite de RegistryClient antes de evaluar los cambios de tipos. Se considera terminado cuando los comentarios son precisos, los tipos de los adaptadores reflejan a sus consumidores y la cobertura demuestra que los fallos de GetRegistry no reintentables que no sean 404 se vuelven a lanzar.