bug: normalize filenames in reports (.f90.f90, double slashes) #1122
Description
Category: bug
Priority: P1
PROBLEM: Reported filenames contain duplicated extensions (e.g., *.f90.f90) and double slashes in paths, reducing clarity.
EVIDENCE:
- coverage.md includes entries like src_utils_strings_string_utils.f90.f90
- Runtime logs show build//gfortran_... (double slash)
SOLUTION:
- Normalize filename extraction from .gcov; strip duplicate extensions/tool suffixes
- Normalize path joins
- Add tests for clean filename rendering