ci: use local mcp-publisher for login step

Author: masnwilliams

.github/workflows/publish-mcp.yml

@@ -39,7 +39,7 @@ jobs:
       - name: Login to MCP Registry
         run: |
           echo "${{ secrets.MCP_PRIVATE_KEY }}" > key.pem
-          mcp-publisher login dns -domain onkernel.com -private-key-file key.pem
+          ./mcp-publisher login dns -domain onkernel.com -private-key-file key.pem
 
       - name: Publish to MCP Registry
         run: ./mcp-publisher publish