Adds operator-only endpoints for discovering organism capabilities:
- GET /api/v1/capabilities - list all listeners
- GET /api/v1/capabilities/{name} - detailed info with schema/example
These are REST-only for operators. Agents cannot access them -
they only know their declared peers (peer constraint isolation).
10 new tests for introspection functionality.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>