v0.3.1

Changed

• release.yml collapsed three jobs into one — release, publish-crates, and publish-npm previously ran on three separate runners. Each step is sub-minute work, so two of those runners were paying the ~30s boot cost for nothing. They're now sequential steps in a single publish job (saves ~1 minute of wall-clock per tag and avoids the multi-runner artifact-download dance).
• python.yml no longer auto-builds on tags — PyPI publishing is still commented out in this file, so every tag was producing five sets of wheels that nothing consumed. Switched the trigger to workflow_dispatch only; re-enable the tag trigger once PyPI publishing is wired up.

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