Maintenance release. No configuration, API, or workspace migration is needed.

- Updates the Servicepack baseline to v1.9.3, including its current security
  maintenance.
- Keeps Peen's dependency policy and byte-exact test fixtures project-owned, so
  future framework updates do not replace them.
- Makes the command process-group test wait for the forked process PID to be
  written before stopping it. This removes a timing-dependent CI failure.