Unity connects to specified MCP server URL using env variable #489
Description
If Unity Editor starts with UNITY_MCP_SERVER_URL env variable Startup must automatically enforce the active connection to the provided URL and port.
The env variable must be added and used a C# constant in a proper location with other constants.
Need to investigate and to research potential problem. When Unity reloads domain multiple times during active workflow with C# scripts changes, it will trigger Startup script to execute each time. Switching PlayMode / EditMode in Unity Editor also triggers domain reload. Need to be sure that the second unnecessary connection will not be started, and no other additional garbage won't be generated.
Need to cover this new feature with tests.