fix: compute release bumps

[satyaborg]

Summary

• Change release.sh to accept patch, minor, or major instead of a manually supplied version.
• Compute the next SemVer value from VERSION and show current/next values in dry-run output.
• Update docs and tests for bump-based releases.

Test plan

• bash tests/devloop_test.sh
• ./release.sh patch --dry-run
• ./release.sh minor --dry-run
• ./release.sh major --dry-run
• ./release.sh 0.1.1 --dry-run
• git diff --check