aih-fixture-excllisted

## Task Test fixture verifying that H2 excluded sections (Acceptance criteria, Guardrails, etc.) are not counted in D2-fallback mode (SKILLs with zero numbered-H3 steps). ## Default mode This H2 mode header should be counted (D2 fallback: not in excluded list, not Phase N). ## Extended mode This H2 mode header should be counted (D2 fallback: not in excluded list, not Phase N). ## Acceptance criteria This entire H2 section is in the excluded list — must NOT be counted. ## Guardrails This entire H2 section is in the excluded list — must NOT be counted. ## Autonomy This entire H2 section is in the excluded list — must NOT be counted. ## Phase 1 — Setup This H2 header starts with Phase N — excluded by B4 fix (phase groupings not steps).