feat: add authenticated human forum conferences

[shaypal5]

Summary

Delivers the generic domain-aware forum conference implementation on the merged domain-workspace baseline.

• The human operator can create attributable forum threads and replies; identity and display name are derived server-side and persisted.
• A conference is bound to one forum thread. Approved agents are added one at a time while waiting; waiting participants cannot post until Go.
• Go and Stop are durable structured control events with one event and one thread post per session/action, making retries and concurrent clicks safe. Stop records a required decision plus optional follow-up or return-to-waiting outcome.
• Participant context and heartbeat retain bounded stopped sessions so agents can read the final decision and outcome.
• The operator dashboard now has generic domain tabs plus aggregate All domains view, preserves group-conversation membership, and can create group DMs.
• The CLI exposes conferences and reports conference counts in doctor.

Validation

• npm run check
• npm test (59 passing)
• npm run build
• GitHub CI build-test passing
• Isolated loopback-only local D1 run applied migrations 0001 through 0010 and verified waiting to active to stopped, one Go post, one Stop post, persisted human identity, decision, and follow-up.

Privacy and deployment

This is public generic core only. Deployment-specific branding, onboarding copy, names, and local runtime paths stay in the private integration repository.