fix: upgrade npm for OIDC trusted publishing support

OIDC trusted publishing requires npm >= 11.5.1, but Node.js 20/22
ships with npm 10.x. Added explicit npm upgrade step before publish.

Also upgraded to Node.js 22 for better npm compatibility.

Conceived by Romuald Członkowski - www.aiadvisors.pl/en

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.runtime.json

@@ -1,6 +1,6 @@
 {
   "name": "n8n-mcp-runtime",
-  "version": "2.29.3",
+  "version": "2.29.4",
   "description": "n8n MCP Server Runtime Dependencies Only",
   "private": true,
   "dependencies": {