fix: simplify npm publishing to use latest tag only

- Remove stable tag complexity from workflow
- Publish directly to latest tag (default for npx)
- Update documentation to reflect single tag approach

.github/workflows/manual-release.yaml

@@ -146,10 +146,10 @@ jobs:
             echo "📝 Version bump and tag were created successfully."
           fi
 
-      - name: Publish to NPM with stable tag
+      - name: Publish to NPM
         env:
           NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}
-        run: npm publish --tag stable
+        run: npm publish
 
       - name: Create GitHub Release
         uses: actions/create-release@v1
@@ -165,7 +165,7 @@ jobs:
       - name: Summary
         run: |
           echo "🎉 Successfully released v${{ steps.version.outputs.new_version }}!"
-          echo "📦 Published to NPM with @stable tag"
+          echo "📦 Published to NPM with @latest tag"
           echo "🏷️ Git tag: v${{ steps.version.outputs.new_version }}"
           echo "✅ Users running 'npx bmad-method install' will now get version ${{ steps.version.outputs.new_version }}"
           echo ""