#7397 fix(agent): ignore empty advanced MCP bindings

Summary

• treat blank MCP Server (Advanced) bindings as inactive
• avoid MCP discovery and tool creation until a server ID is configured
• preserve fail-fast behavior for malformed non-string bindings

Type of Change

• Bug fix

Testing

• 163 focused MCP and Agent tests passed
• lint and all 45 repository audits passed

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)