daily-fix: 6a.5 gate asserts git-tree reachability

Overview / Motivation

Auto-filed by /daily 2026-07-16 from transcript mining (#1434 session 027e29e8, ~04:50-05:39Z).

Goal

Make the pre-dispatch artifact gate catch uncommitted inputs before a git-clone-only lane boots.

Workflow gap

• Bug observed: the Step 6a.5 carry-over-artifact gate reported 'all carry-over artifacts resolve' while checking LOCAL resolution only — the #1434 cell manifest was uncommitted/untracked, so the git-clone GCP lane never staged it and all 12 runs failed TWICE with FileNotFoundError (#734 family; ~2 boot cycles + 24 run-attempts lost, fixed by committing the manifest f9f1002797)
• Why it is a workflow gap: The #734 clause already names git-tree reachability as the reuse requirement; the gate that is supposed to enforce it checks the wrong predicate (local presence).
• Confidence (emitter): high (24 failed run-attempts today; fix confirmed by commit f9f1002797)
• verified-at-filing: incident in #1434 transcript (12 runs x2 FileNotFoundError; gate had reported all-resolve); commit f9f1002797 verified resolving via git log; grep -n '6a.5' .claude/skills/issue/SKILL.md locates the gate block (git-tree predicate absent — planning verifies the exact block)

Proposed change (candidate diff sketch — refine in planning)

make the 6a.5 gate additionally assert each plan-referenced input under eval_results/ or data/ is git-tree-reachable at the dispatch tip when the lane is git-clone-only (per the existing #734 clause in artifact-reuse)

Scope / surfaces

• Primary target: .claude/skills/issue/SKILL.md
• Grep the workflow surface for the pattern before editing and update every hit; list them in the plan.

Constraints / invariants

• scripts/workflow_lint.py --check-asks passes; ruff on touched files passes.
• This session runs under a workflow_fix_target: Provenance line — it MUST NOT auto-route its own subagents' workflow-fix candidates (recursion guard).

Provenance

• fingerprint: 6fa92d54950b