chore: improve npm publish workflow

[michaelva]

Summary

• Simplified npm publish workflow to use the current branch instead of requiring a ref input
• Added dev version type option alongside patch, minor, major
• Version type now controls versioning behavior (dev = timestamped, others = bump)
• npm tag still tied to branch (main → dev, preview → latest, other → experimental)
• Added pnpm install for llumiverse submodule to fix workspace protocol resolution
• Added repository field to create-plugin package for npm provenance verification
• Improved script documentation with README

Test plan

• Tested dry-run mode on feature branch
• Verify dry-run passes on preview branch
• Test actual publish from main branch

🤖 Generated with Claude Code