refactor(prompt): rename subcommands and add frontmatter output

- Rename: user→usage-reference, author→workflow-authoring, adapter→adapter-developing
- Remove: developer (content lives in CLAUDE.md)
- All prompts output complete SKILL.md with YAML frontmatter
- Setup instructions simplified: uwf prompt bootstrap > SKILL.md
- Remove all bun references, use pnpm/npm
- Fix CLAUDE.md: fixed→independent versioning
- Delete old reference files (user/author/developer/adapter)

Closes #66

CLAUDE.md

@@ -266,7 +266,7 @@ node scripts/publish-all.mjs --dry-run    # preview without publishing
 
 - `workspace:^` dependencies resolve to `^x.y.z` on publish
 - Publish order defined in `scripts/publish-all.mjs` (dependency order)
-- Changesets config: `.changeset/config.json` (fixed mode, public access)
+- Changesets config: `.changeset/config.json` (independent versioning, public access)
 
 ### End-to-end: Author → Register → Run