feat(dag): harness batch — parallel writers, REJECT checkpoints, union-arg tolerance - #303

Summary

Promotes the dev integration layer to the main quality gate. Content delta is zero beyond the merge history (verified: git diff origin/dev...origin/main is empty); this PR exists to run the full gate (Typecheck + Unit Tests + E2E linux/windows) over the harness batch before release.

What lands (issues treated as specs)

• fix(tool): qwen-family models stringify nested-union tool parameters — workflow tool unusable #297 / PR fix(tool): tolerate stringified nested-union tool arguments #298 — fix(tool): lenient retry in the tool decode wrapper repairs qwen-family models stringifying nested-union tool arguments; the workflow tool becomes usable on those models. Precondition of the whole batch.
• spec(dag): parallel workspace writers with implementation evidence aggregator #293 / PR feat(dag): run unordered workspace writers in parallel with an implementation aggregator #299 — feat(dag): unordered workspace writers compile truly parallel; one read-only aggregator node per parallel implementation-review route (loud write-set-overlap gate, union changed-files, single convergence-point fingerprint); verify rewiring + fingerprint binding; total-ordered chains byte-identical. Runtime/review-lifecycle untouched. ADR-0002 included.
• spec(dag): unblock the REJECT checkpoint — a rejected review completes the workflow (A1) #294 / PR fix(dag): complete workflows at rejected review checkpoints instead of failing them #300 — fix(dag): workflows settle COMPLETED (not failed) at REJECT checkpoints so the designed reopen-extend path becomes reachable; explicit completion shortcuts keep the review gate (skipReviewGate); status surfaces unresolved_reviews.
• spec(policy): verdict-disposal classifier and explicit tier escalation #296 / PR docs(policy): add verdict-disposal classifier and explicit tier escalation #301 — docs(policy): verdict-disposal findings classifier in the Verdict Disposal Contract; tier escalation promoted from hint to explicit rule; risk-only tier discriminator.
• docs: reconcile harness review with landed implementation #302 — docs: harness review reconciled with landed implementation (appendix B decision→PR table).

Cross-repo companion (already merged)

opencode-dag-config PR #9: runtime-compat.json pinned to the parallel-writers merge SHA ebc5ad089, triple-disjoint write-set contract in the full project-development route, native output-by-reference replacing the hand-rolled delivery contract. Template-validation CI green at the pinned SHA.

Evidence

• dev push CI at the pre-docs: reconcile harness review with landed implementation #302 head: Typecheck + Unit Tests (linux) + E2E (linux/windows) all success.
• docs: reconcile harness review with landed implementation #302 is docs-only and passed the dev PR Typecheck gate.
• Post-merge review: doc↔implementation reconciliation, codebase-design audit (deep modules at existing seams, no shallow additions), PR-report verification — no discrepancies found.

Release plan

After this merges, trigger release-fork.yml on main (workflow_dispatch, create_release) — formal X.Y.Z, marked Latest.