fix(dag): reject ungated reporting checkpoints at authoring

[LeXwDeX]

Incident (2026-08-17)

Workflow dag_fe5ff13ada6fUONA2rH3Pypdf4 ("ultra flow", hand-authored 15-node graph) ran 75 min to completed although every decision checkpoint returned verdict: replan: the design gate rejected the design, yet stage-development spawned 12 ms after the checkpoint settled; all four downstream gates re-rejected and nothing was implemented. Wake batch landed once, at terminal — the parent could never intervene mid-run.

Root cause: hand-authored node graphs carry no condition gates on checkpoint dependents. Block-compiled graphs gate dependents on the verdict (blocks.ts:147,185,236, issue #294 REJECT-checkpoint shape); the authoring check has zero diagnostics for the ungated shape.

Design (grill-settled)

• Semantics: a report_to_parent: true node with dependents is a reporting checkpoint (decision point); dependents must be gated by condition referencing its output. input_mapping does NOT count as gating.
• Severity: dag.invalid error, both deep and standard modes.
• Enforcement point: authoring boundary only (validatePostCompile structural phase, i.e. workflow tool start/validate). Dag.create / replanStructuralDiagnostics intentionally untouched — preserves wake-chain runtime semantics and reopen-extend (issue spec(dag): unblock the REJECT checkpoint — a rejected review completes the workflow (A1) #294).
• Coverage: start action only. Replan/extend fragment gap recorded, deliberately not fixed here.
• Legacy advisory wake chains: deprecated in new graphs, zero runtime change for running ones.
• Saved ungated specs rejected on re-start — accepted; diagnostics carry three fix hints.
• Docs: reporting checkpoint glossary entry in dag CONTEXT.md + ADR (records rejected alternatives: runtime enforcement H2 — verdict vocabulary open, ACCEPT path must not wait; terminal-wake verdict aggregation H3 — shelved).

Acceptance

• New test test/dag/dag-checkpoint-gate.test.ts (6 cases: ungated rejected; condition-gated accepted; leaf accepted; rtp=false accepted; node_defaults inheritance flagged; wrong-dependency gate flagged)
• Incident spec repair-memory-write-path.yaml replay → start rejected with 5 diagnostics matching the incident's 5 checkpoint→stage pairs
• test/dag/ full suite green (baseline 556 pass), bun typecheck clean
• Audit: 14 curated block workflows unaffected; hits limited to ultra-flow-route.yaml + release-route.yaml (see config-repo issue)

Status

Implementation + tests done on fix/checkpoint-gating (worktree /private/tmp/oc-dag-checkpoint-gate, based on dev @16f9add17). Remaining: CONTEXT.md glossary, ADR, workflow-tool description line, commit, PR → dev. PR title: fix(dag): reject ungated reporting checkpoints at authoring.

[LeXwDeX]

Merged via PR #325 (merge commit 6058718). Authoring now rejects ungated reporting checkpoints at start/validate; incident shape replayed and rejected with 5 diagnostics. See ADR-0003.