Ignore the nmon-dev binary

It was committed by accident in the M3 work and removed from the remote;
ignoring it keeps a local build from being added again.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017TuKgyKve2XLFtrrXWMi2w

.gitignore

@@ -17,3 +17,4 @@ deploy/ansible/vars.yml
 
 # MCP Vector Search index directory
 .mcp-vector-search/
+/nmon-dev