add stable release command

[lancekrogers]

Summary

• make just release stable the canonical one-command stable release entrypoint
• keep just release tag vX.Y.Z for explicit version tags, but make it push the tag too
• update release docs to point at the just command instead of manual git steps

Validation

• just release
• just release current
• just release check

Note

• this PR does not create a release tag; it only makes the release flow consistent and discoverable