Expand path mapping and stored path validation coverage

[olxgdm]

Summary

• Add regression coverage for storage-relative path validation with slash, backslash, mixed separator, rooted, malformed, and traversal cases.
• Expand path mapping tests for POSIX cleanup, Windows drive-letter slash variants, relative inputs, and generated storage paths.
• Extend Registry and StorageManager unsafe stored path coverage at their integration boundaries.

Closes #61

Verification

• cmake --build build
• ctest --test-dir build -R "PathFileUtils|Registry|StorageManager" --output-on-failure
• ctest --test-dir build --output-on-failure

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud