chore(ei-parity): freeze certification corpus

[Roddygithub]

Summary

• freeze the 35-log Elite Insights v3.26.0.0 corpus with private-artifact hashes
• validate the full corpus before parsing and emit an aggregate, non-personal baseline
• document and test certification failure paths and atomic baseline generation

Verification

• uv run pytest tests/scripts/test_ei_diff.py -q (29 passed)
• uv run ruff check scripts/ei-parity/ei_diff.py tests/scripts/test_ei_diff.py
• uv run ruff format --check scripts/ei-parity/ei_diff.py tests/scripts/test_ei_diff.py
• uv run python scripts/ei-parity/ei_diff.py --json scripts/ei-parity/corpus-baseline.json (35 logs, 133 differences, 13 buckets)

Scope

Only story 1 artifacts are included. Local BMAD installation files are intentionally excluded.