why: release the FastMCP axis taxonomy — tools classified on axes a
project declares, reading tags, MCP annotations, or tool meta.

what:
- Bump all workspace packages 0.1.0a37 → 0.1.0a38
- Date CHANGES entry for 0.1.0a38 (2026-08-30) and write its release
  lead paragraph
- Add 0.1.0a39 unreleased header