chore(audit): remove duplicate import json in src/code_path_audit.py

The import statement appeared twice in quick succession (lines 655 and 658).
Both were identical and contributed nothing. Removed one. No functional change.

Verification:
- grep -c '^import json' src/code_path_audit.py = 1
- uv run python -c 'from src import code_path_audit' returns OK
- 124 tests in tests/test_code_path_audit*.py pass

src/code_path_audit.py

@@ -654,9 +654,6 @@ def compute_decomposition_cost(
 
 import json
 
-
-import json
-
 def read_input_json(path: str) -> Result[dict]:
  """Read a JSON file and return Result[dict].