Add e2e script for agentic env gen

[qianl-nv]

Summary

Add environment_generation_runner for running the agentic environment generation end to end

Detailed description

• What was the reason for the change?
  We need an entry point to run the full agentic env gen pipeline for integration testing.

• What has been changed?
  A new script is added to run the agentic env gen. It does the following steps:

  • Takes user prompt from CLI, pass through EnvGenAgent to generate EnvIntentSpec
  • EnvIntentSpec compiles to UnresolvedArenaEnvGraphSpec (asset match into registry), then ArenaEnvGraphSpec (constraints populated). The final ArenaEnvGraphSpec serialized to yaml.
  • ArenaEnvGraphSpec is loaded back from yaml, and build into an ArenaEnvironment
  • Run zero_action policy simulation for visualizing output (with RelationSolver initializing layouts)

• What is the impact of this change?

  • Known limitations: no support for ObjectSet or ObjectReference. No user in the loop editing.