Phase 3 (spec-zqb) scope decision: spec_comment is NOT built in Phase 3. Comments belong to Phase 5 (spec-by6), which explicitly defers the comment schema until the Phase 4 review UI settles anchor/resolution semantics. The approve/reject BROWSER UI is Phase 4 (spec-3vz); Phase 3 builds the service-level Merge/Reject orchestration + auto-merge policy (exercised by policy auto-merge, not a human button). Phase 3 deliverables: service.Propose/Merge/Reject/ListProposals, service.Proposal type + proposal URL (<origin>/~owner/space/p/<id>), provenance-trailer commits, db.ListProposalsBySpace, then surfaces: graph adapter (wire Proposals in main.go), mcpsrv spec_propose, and a NEW api/ package for REST PUT /api/v1/spaces/~owner/name/docs/<path> (If-Match + X-Proposal headers). Every write returns {proposal, url}.