Use pyvenv.cfg mtime in cache key instead of file content
Use the pyvenv.cfg modification time as a separate component in the
cache filename digest rather than hashing the full file content. This
is cheaper (stat vs read) while still correctly invalidating the cache
when the virtual environment is recreated.
https://claude.ai/code/session_01XnGrXu7zANvMbh53D2GMU2