fix: support project discovery from git worktrees

[patrickswedish]

Summary

• recognize both .git directories and git worktree pointer files as project roots
• add a regression test for nested paths inside a worktree

Closes #210

Validation

• PYTEST_DISABLE_PLUGIN_AUTOLOAD=1 python -m pytest tests/unit/utils/test_misc.py -q (16 passed)
• python -m pre_commit run --files src/ragger/utils/misc.py tests/unit/utils/test_misc.py

[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