feat: support lazy environment activation in NodeEnvManager

[idoros]

This PR Split worker environment initialization into two phases to support lazy startup:

1. preLoad - spawn worker and set up communication
2. activate - send activate rpc, wait for ready

Changes

• Add lazy parameter to autoLaunch - when true, environments are pre-loaded but not activated until new activateEnvs() is called explicitly
• Fire a new activate rpc call to notify environment
• keep backwards compatibility with WorkerThreadInitializer2.initialize() as a convenience that calls both preLoad and activate