test(audit): behavioral SSDL test locks down effective_codepaths math

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

tests/fixtures/synthetic_ssdl/sample_module.py

@@ -0,0 +1,48 @@
+def func_one(x: int) -> int:
+ if x > 0:
+  x += 1
+ if x > 1:
+  x += 1
+ if x > 2:
+  x += 1
+ return x
+
+
+def func_two(x: int) -> int:
+ if x > 0:
+  x += 1
+ if x > 1:
+  x += 1
+ if x > 2:
+  x += 1
+ return x
+
+
+def func_three(x: int) -> int:
+ if x > 0:
+  x += 1
+ if x > 1:
+  x += 1
+ if x > 2:
+  x += 1
+ return x
+
+
+def func_four(x: int) -> int:
+ if x > 0:
+  x += 1
+ if x > 1:
+  x += 1
+ if x > 2:
+  x += 1
+ return x
+
+
+def func_five(x: int) -> int:
+ if x > 0:
+  x += 1
+ if x > 1:
+  x += 1
+ if x > 2:
+  x += 1
+ return x

tests/test_code_path_audit_ssdl_behavioral.py

@@ -0,0 +1,98 @@
+"""Behavioral SSDL tests for src.code_path_audit_ssdl.compute_effective_codepaths.
+
+Locks down the headline 4.01e22 effective codepaths math against a small
+synthetic fixture so future refactors cannot silently change the formula.
+
+CONVENTION: 1-space indentation. NO COMMENTS.
+"""
+from __future__ import annotations
+
+from src.code_path_audit import (
+ AggregateProfile,
+ CrossAuditFindings,
+ DecompositionCost,
+ FunctionRef,
+ Frequency,
+ FrequencyEvidence,
+ ResultCoverage,
+ TypeAliasCoverage,
+)
+from src.code_path_audit_ssdl import compute_effective_codepaths
+
+
+FIXTURE_FILE = "sample_module.py"
+FIXTURE_SRC_DIR = "tests/fixtures/synthetic_ssdl"
+FIXTURE_FUNC_NAMES = (
+ "func_one",
+ "func_two",
+ "func_three",
+ "func_four",
+ "func_five",
+)
+
+
+def _make_synthetic_profile() -> AggregateProfile:
+ consumers = tuple(
+  FunctionRef(
+   fqname=f"tests.fixtures.synthetic_ssdl.sample_module.{name}",
+   file=FIXTURE_FILE,
+   line=1,
+   role="consumer",
+  )
+  for name in FIXTURE_FUNC_NAMES
+ )
+ return AggregateProfile(
+  name="synthetic",
+  aggregate_kind="typealias",
+  memory_dim="control",
+  producers=(),
+  consumers=consumers,
+  access_pattern="whole_struct",
+  access_pattern_evidence=(),
+  frequency="per_turn",
+  frequency_evidence=(),
+  result_coverage=ResultCoverage(0, 0, 0, 0, ""),
+  type_alias_coverage=TypeAliasCoverage(0, 0, 0, ""),
+  cross_audit_findings=CrossAuditFindings((), (), (), (), ()),
+  decomposition_cost=DecompositionCost(0, 0, 0, "hold", "no data", None, 0, False),
+  optimization_candidates=(),
+  is_candidate=False,
+ )
+
+
+def _make_candidate_profile() -> AggregateProfile:
+ f = FunctionRef(
+  fqname="tests.fixtures.synthetic_ssdl.sample_module.func_one",
+  file=FIXTURE_FILE,
+  line=1,
+  role="consumer",
+ )
+ return AggregateProfile(
+  name="synthetic_candidate",
+  aggregate_kind="typealias",
+  memory_dim="control",
+  producers=(),
+  consumers=(f,),
+  access_pattern="whole_struct",
+  access_pattern_evidence=(),
+  frequency="per_turn",
+  frequency_evidence=(),
+  result_coverage=ResultCoverage(0, 0, 0, 0, ""),
+  type_alias_coverage=TypeAliasCoverage(0, 0, 0, ""),
+  cross_audit_findings=CrossAuditFindings((), (), (), (), ()),
+  decomposition_cost=DecompositionCost(0, 0, 0, "hold", "no data", None, 0, False),
+  optimization_candidates=(),
+  is_candidate=True,
+ )
+
+
+def test_effective_codepaths_synthetic() -> None:
+ profile = _make_synthetic_profile()
+ result = compute_effective_codepaths(profile, src_dir=FIXTURE_SRC_DIR)
+ assert result == 40
+
+
+def test_effective_codepaths_candidate_returns_zero() -> None:
+ profile = _make_candidate_profile()
+ result = compute_effective_codepaths(profile, src_dir=FIXTURE_SRC_DIR)
+ assert result == 0