Add buildroom autonomy loop bridge

[Danservfinn]

Summary

• add dry-run/default Kanban bridge for Control Room drafts with explicit apply mode and idempotency keys
• add non-destructive retention follow-up emitter and generated retention payload
• add one-command buildroom healthcheck/canary and operating-loop docs
• add focused tests for dedupe, apply idempotency, retention follow-ups, and quick healthcheck

Verification

• PR Add buildroom Control Room cron loop #4 merged first: merge commit 1a420f8
• /opt/homebrew/opt/python@3.14/bin/python3.14 tools/kurultai/buildroom/scripts/buildroom_healthcheck.py: PASS
• focused pytest via healthcheck: PASS
• scoped leakage scan: 0 findings

Local operating-state note

• applied current safe Control Room Kanban drafts locally with dedupe
• created Hermes Kanban tasks t_256b5beb and t_4d85340c