Editor toolbar gains Play/Stop (Ctrl+P) with UE semantics:
- Play: serialize current scene to an in-memory YAML snapshot via new
SceneSerializer::SerializeToString, switch display to kDisplayDirect
(primary camera entity renders), unfreeze time (timeScale 0 -> 1)
- Stop: DeserializeFromString atomically rebuilds the pre-play scene,
back to kDisplayViewport (editor camera), refreeze time; selection
cleared and gizmo drag reset since all entity handles dangle
- SceneSerializer refactored: SerializeDoc/ParseRoot shared by file
and memory variants; file Save/Load behavior unchanged
- Running state disables gizmo + editor hotkeys in the viewport (input
goes to game scripts), draws yellow PLAYING hint and a no-camera
warning; File->Save/Load disabled while playing (UE behavior)
Physics bodies/constraints/characters and script instances are
reconciled automatically by the existing per-frame sync on restore.
atdunbg
2577809ee4