[codex] make GameObject read-back honest

[Daliys]

Summary

• expand get_game_object read-back payload with transform state and compact component data
• keep script-write and Play Mode readiness probes busy during Unity reload/transition windows
• add regression coverage for verifying set_transform and component additions through get_game_object

Why

set_transform could report success while the cheap read path only returned name and instance_id, so agents could not verify the state they just wrote without heavier component inspection. The integration suite also exposed races where script writes and Play Mode transitions reported ready too early.

Validation

• Assets/NexusUnity/scripts/prepush-validate.sh --full passed: static validation, quick live smoke, and 11/11 Python integration tests
• push pre-hook passed: static validation and quick live smoke