Venvs in OS temp dirs silently lose files after days

A Python venv kept under a macOS /private/tmp scratch directory broke between sessions: pyvenv.cfg vanished (sys.prefix fell back to the system Python) and numpy lost its __init__.py, so openpyxl failed with "module 'numpy' has no attribute 'short'". The OS temp cleaner deletes old files individually, leaving a half-empty package tree rather than an obviously missing venv. Restoring pyvenv.cfg is not enough; recreate a fresh minimal venv (e.g. just openpyxl and formulas) instead of debugging the partial one. When reviewing budget spreadsheets edited by another agent, also cross-check that priority rankings agree with which items the alternate budgets drop; they drift apart easily.