feat: set up npm publishing infrastructure

Configures DevClaw package for publishing to npm registry with automated
GitHub Actions workflow and comprehensive publishing documentation.

Changes:

1. package.json:
   - Added publishConfig with access: public (required for scoped packages)
   - Already has correct name: @openclaw/devclaw
   - Version: 0.1.0 (ready for initial release)
   - Files array properly configured (dist/, roles/, docs/)
   - prepublishOnly script ensures build before publish

2. GitHub Actions Workflow (.github/workflows/npm-publish.yml):
   - Triggers on release publication
   - Manual workflow dispatch option with tag input
   - Uses NPM_ACCESS_TOKEN secret for authentication
   - Includes npm provenance for supply chain security
   - Publishes as public package
   - Provides summary output after publication

3. Publishing Documentation (PUBLISHING.md):
   - Comprehensive guide for all publishing methods
   - Automated publishing via GitHub releases (recommended)
   - Manual workflow trigger instructions
   - Local publishing fallback
   - Dry-run testing procedures
   - Version management guidelines
   - Troubleshooting common issues
   - Post-publishing checklist

Configuration Details:
- Package name: @openclaw/devclaw (scoped)
- npm account: laurentenhoor
- Access: public (free for scoped packages)
- Provenance: enabled for transparency
- Node.js: >=20 required

Ready for Initial Release:
To publish the first version:
1. Verify NPM_ACCESS_TOKEN is set in GitHub secrets
2. Create and push tag: git tag v0.1.0 && git push --tags
3. Create GitHub release from tag
4. Workflow automatically builds and publishes to npm

Addresses issue #130

package.json

@@ -32,6 +32,9 @@
     "roles/",
     "docs/"
   ],
+  "publishConfig": {
+    "access": "public"
+  },
   "scripts": {
     "build": "tsc",
     "check": "tsc --noEmit",