Mirrors the canonical workflow shipped on internal#120 + #122. Same
shape: pull_request_target on closed, base.sha checkout, structured
JSON event to runner stdout that Vector ships to Loki on
molecule-canonical-obs.
REQUIRED_CHECKS env declares both molecule-core/main protected
contexts (sop-tier-check + Secret scan). Mirror against branch
protection if either is added/removed.
Verified end-to-end on internal: synthetic force-merge of internal#123
emitted incident.force_merge with all expected fields, indexable in
Loki via {host="molecule-canonical-1"} |= "incident.force_merge".
Tier: low (CI workflow, no platform code path).
