Harden recursive directory import edge cases

[olxgdm]

Summary

• Harden recursive directory import logging and skip handling for symlinked directories and traversal failures.
• Report skipped already-tracked files when a directory import also adds new files.
• Add regression coverage for symlinked directories, special files, and AddCommand CLI output.

Closes #60

Verification

• cmake --build build
• ctest --test-dir build -R "AddCommand" --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
88.6% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud