## Why
Python's `ProcessPoolExecutor` queries `SEM_NSEMS_MAX` through `sysconf`, which reads the `kern.sysv.semmns` sysctl on macOS.
## What changed
- Allow reads of `kern.sysv.semmns` in the base Seatbelt policy.
- Verify `/usr/bin/getconf SEM_NSEMS_MAX` succeeds with both read-only and workspace-write sandbox policies.
GitOrigin-RevId: ab3ae92dc8991729f90a47c1994eedb6c7a2b9cd