Add scripts/release.sh that infers bump type from conventional commits
(major/minor/patch), bumps package.json, commits, tags, and pushes.
Includes safety checks for branch, clean tree, and remote sync.
Also adds a workflow_dispatch GitHub Actions workflow (bump.yml) and
Makefile targets (release, release-patch, release-minor, release-major).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>