Compact matrix specs previously required a positive exact cap and always injected incremental_exact_max_affected_paths. A default-versus-default historical comparison therefore had to overwrite candidate policy with one shared cap.
Allow null in scenarios[].exact_caps to omit the config override, omit the capability identity key, retain exact_cap=null in parameters, and label the cell capdefault. Positive integers keep the existing explicit cap-sweep behavior. Document both forms in docs/BENCHMARK_CAMPAIGN.md.
Tests: uv run python -m unittest tests.test_benchmark_campaign -v (16 passed); uv run ruff check scripts/run-benchmark-campaign.py tests/test_benchmark_campaign.py (passed); git diff --check (passed).
Signed-off-by: Andrew Hundt <ATHundt@gmail.com>