tempfile.gettempdir() on macOS returns /var/folders/xx/yy.../T/ (~49 chars).
Combined with bu-{64-char-name}.sock that exceeds the 104-byte sun_path
limit on macOS (108 on Linux), causing daemon startup to fail.
Pre-PR upstream hardcoded /tmp; this restores that for POSIX. Windows is
unaffected (uses TCP, not AF_UNIX).
Cut ipc.py from 127 to 68 lines (-46%) by removing restated docstrings and
keeping only load-bearing inline comments (path-traversal guard, uv-Python
AF_UNIX gating, Windows .port-file role). Same logic, same call sites.
Rename ipc -> _ipc per Python convention for internal modules. The IPC
plumbing is only called by daemon/admin/helpers; agents reading helpers.py
should not be pulled into transport details. Callers do 'import _ipc as ipc'
so internal ipc.foo references stay unchanged.
Alezander9