Adds a small synthetic fixture (tests/fixtures/synthetic_ssdl/) with 5
consumer functions, each containing 3 explicit if-statements. The fixture
is self-contained and does not depend on the live src/ tree.
The new test tests/test_code_path_audit_ssdl_behavioral.py has 2 tests:
- test_effective_codepaths_synthetic: builds an AggregateProfile with 5
consumers pointing at the fixture's 5 functions, calls
compute_effective_codepaths, asserts the result is 40 (= 5 consumers x
2^3 branches per function).
- test_effective_codepaths_candidate_returns_zero: asserts that an
AggregateProfile with is_candidate=True returns 0 (the SSDL early-exit
guard for candidate aggregates).
This locks down the SSDL effective-codepaths math so future refactors of
compute_effective_codepaths() or count_branches_in_function() cannot
silently change the formula without a failing test.
Verification:
- uv run pytest tests/test_code_path_audit_ssdl_behavioral.py -v -> 2 passed
