Forge Reliability Loop: sensor + runbook framework (umbrella)

feature_id: FEAT-FORGE-RELIABILITY

Umbrella ticket for the Operant Forge Reliability Loop. See /home/user/workspace/stuck_state_taxonomy.md.

Children: OPER-38 through OPER-46. Success: 0 orphan AWAITING_HUMAN 7d, 0 CLEAN PRs >2h, dispatcher error dominance <80 percent.