Grouped transform mutation contract

Perastage treats each scene node's editable world matrix as the visible placement and stores a local matrix for MVR hierarchy persistence.

Corrected user-editing paths

• Fixture, Truss, Support, and SceneObject table transforms use the shared exact-world mutation boundary.
• Primitive SceneObject placement and object-level scale changes use the same exact-world boundary; geometry-entry scale remains geometry-local.
• scene.transform.batch resolves every declared kind/UUID exactly, without interactive child promotion. Explicit GroupObject components reuse the same descendant synchronization boundary and retain ordered child/group updates.
• Fixture-to-Support conversion preserves UUID, world/local transforms, parent metadata, and changes the existing GroupObject child-reference type.
• Table deletion uses the typed core removal service, removes parent child references, and recursively prunes groups that become empty.

Deleting a GroupObject explicitly deletes its complete subtree. Deleting leaf nodes preserves non-empty ancestors and prunes empty ancestors. This is a Perastage editing policy; it does not change MVR import hierarchy semantics.

Reviewed-safe paths

• MVR import builds world transforms from parent-world and local matrices.
• Grouping, ungrouping, and reparenting preserve world placement through the scene-grouping service.
• selected-Truss replacement preserves world/local/parent metadata.
• SceneObject-to-Truss conversion preserves transform metadata and repoints the GroupObject child-reference type.
• Undo and Redo restore complete scene snapshots rather than replaying direct transform writes.
• Renderer, loader, and view caches contain derived transforms and do not own editable hierarchy state.

Additional mutation paths

• Duplication constructs independent top-level nodes and intentionally clears inherited hierarchy ownership before insertion.
• Clipboard paste restores complete serialized scene records; it does not apply partial world-matrix edits to existing grouped nodes.
• Alignment and distribution use the interactive scene-grouping boundary, so grouped Trusses promote while other node types remain exact.
• Fixture and Truss replacement preserve the instance world/local matrices and parent metadata while changing type-level resource fields.
• Fixture-to-Support and SceneObject-to-Truss conversions now preserve or repoint hierarchy ownership through their owning conversion services.
• Grouping, ungrouping, Magnet commit/detach, and explicit reparenting use core hierarchy helpers that preserve world placement and rebuild local matrices.
• Primitive object placement uses the exact transform boundary; geometry-entry transforms are intentionally local geometry data rather than scene-node placement.
• Direct map erasure remains only in construction/import/reset code or inside the hierarchy-aware removal service. Table deletion no longer erases scene nodes directly.
• Undo and Redo replace the complete scene snapshot, including both transform matrices and GroupObject ownership, so no incremental hierarchy repair is required during restoration.

Permissive MVR reading, renderer/model-loader transforms, view caches, and derived geometry matrices were reviewed but intentionally left unchanged because they do not mutate editable scene-node hierarchy state.