why: Ship sphinx-gp-mermaid, the build-time Mermaid diagram
package.

what:
- Bump the workspace from 0.0.1a31 to 0.0.1a32 across every
  package, source version constant, lockfile, and tests
- Date the 0.0.1a32 CHANGES entry and open the 0.0.1a33
  unreleased block