Summary

Adds regression tests for KOTOR install directory detection after PR #151 switched is_kotor_install_dir to CaseAwarePath in three call sites.

Risky behavior now covered

• Install detection used by diff CLI, patching tools, and TSLPatcher diff engine to decide whether a path is a game root (chitin.key present).
• Case-insensitive paths on POSIX: mismatched install directory name and mismatched chitin.key filename (e.g. CHITIN.KEY).
• Negative cases: missing path, empty directory, and file (non-directory) paths.

Test files added/updated

• Libraries/PyKotor/tests/common/test_is_kotor_install_dir.py (new, 18 parametrized tests across cli_utils, patching, and diff.engine)

Why this reduces regression risk

These helpers gate high-blast-radius flows (patching installs, diff against game roots). A regression in CaseAwarePath integration could silently treat valid installs as invalid on Linux/macOS mod layouts with case drift. The tests lock the intended behavior without requiring a full KOTOR installation fixture.

Validation

QT_QPA_PLATFORM=offscreen uv run --directory Libraries/PyKotor pytest --import-mode=importlib tests/common/test_is_kotor_install_dir.py -v

18 passed (POSIX case tests skipped on Windows by design).