HierarchyPanel walks IWorld.Roots/GameObject.Children recursively as
ImGui tree nodes, clicking one sets EditorState.Selected — the shared
selection the not-yet-built Inspector panel will read from the same
instance. PushID(go.GetHashCode()) scopes each node's ID by object
identity rather than name, since nothing stops two sibling GameObjects
sharing a Name and ImGui's default label-based IDs would otherwise merge
their open/selected state.
Also gives samples/WindowDemo/scene.json a child GameObject (offset,
half-scale, parented under Quad) — the existing scene only had one root,
nothing to show a tree with. Verified by screenshot: both quads render at
their correct composed WorldMatrix (the child visibly smaller and offset,
confirming parent/child composition is still correct through this
change), and Hierarchy lists "Quad" as a collapsible node.
Full suite still green: 65 tests.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N1qPfzq8TDCUMFMV3UwV5N
