feat(registry): community-mirror lifecycle + upsert client (JS #2183/#2187 parity)

[bokelley]

Gap

JS SDK adcp-client#2183 / #2187 added a community-mirror lifecycle for adagents catalogs: publish / get / list persisted mirrors (PUT/GET /api/registry/mirrors/:platform) plus upsertCommunityMirrorAdagents with platform inference.

Python's RegistryClient (src/adcp/registry.py) has create_adagents (POST /api/adagents/create — the generator-only equivalent) but no persisted-mirror methods (grep for registry/mirrors / community_mirror returns nothing).

Scope

Add to RegistryClient, matching the JS route/body shapes (confirm exact shapes from the JS PRs before implementing):

• publish_community_mirror_adagents(...) → PUT /api/registry/mirrors/:platform
• get_community_mirror_adagents(...) → GET /api/registry/mirrors/:platform (return None on 404)
• list_community_mirror_adagents(...)
• an upsert_community_mirror_adagents(...) helper with platform inference

Parallels the existing create_adagents HTTP-client pattern.

Notes

• Reference: adcontextprotocol/adcp-client#2183, #2187.
• Distinct from Python SDK: wholesale feed mirror helper for products/signals #900 (wholesale product/signal feed mirror — data sync, different endpoint/purpose).
• Single-agent triage verification — confirm the JS route/body shapes before prioritizing.
• Filed no-triage.

[bokelley]

Upstream spec gap filed: adcontextprotocol/adcp#5384. The community-mirror endpoints are not in the registry OpenAPI (static/openapi/registry.yaml), which is why PR #929 types them as dict[str, Any]. Once the spec defines them, regenerate adcp.types.registry via make regenerate-registry and retype the client to use the generated models.