test: raise temp file manager coverage to 92%

[Patrik652]

Summary

• add tests/unit/test_temp_file_manager.py
• cover create/cleanup lifecycle, disabled-cleanup behavior, tracked+orphan cleanup, aggregated error handling, and destructor cleanup path
• improve confidence in temp file lifecycle semantics across services

Test Plan

• PYTHONPATH=. .venv/bin/ruff check src/services src/cli tests/unit/test_temp_file_manager.py
• PYTHONPATH=. .venv/bin/mypy src/services src/cli
• PYTHONPATH=. .venv/bin/pytest -q

Result

• 360 passed, 0 skipped, 2 warnings
• total coverage: 85%
• src/services/temp_file_manager.py: 92%