D.1 (complete_task refused without writeback) and D.2 (propose_plan
auto-appends writeback step) shipped in 3de359b (v0.5.1), e2e-validated
against the live agent. The knowledge loop is now structurally closed —
no blockers remain. Remaining items (F.1, F.2, C.1, C.2, B.4-B.6, E.1,
E.2) are all friction/cosmetic.