EPIC: foreign-repo gate validation (dirty ledger)

[cansirin]

Dirty-ledger fixture for #368 FAIL test — one child intentionally omits acceptance criteria.

User stories

1. As an adopter, I want a structurally-dirty ledger to FAIL the gate and flip nothing.

Dependencies

Phase 1

• Dirty child — missing acceptance criteria (ZERO_AC) #4

[cansirin]

review-plan: FAIL — ledger has hard defects

Epic #5's ledger has 1 hard defect(s); no child was flipped.
Each must be resolved before the gate can flip status:planned → status:triaged:

• ZERO_AC (Dirty child — missing acceptance criteria (ZERO_AC) #4) — Child Dirty child — missing acceptance criteria (ZERO_AC) #4 has zero acceptance criteria.