[qt/qt/qtquick3d]: Summary of bulk changes made

Git repository change summary for qt/qt/qtquick3d
Pushed by mirror-service into branch '6.12'.
Changed from 2c497a0c213fe8d814b73e5880a1e643fd6f194d to 0dfa4e269cfa0be87fc823e74e6af4b62cb7c973
Acknowledgement was received that this change introduces only existing code that has been pushed to another public open source repository.

This change contains the following new commits:

Git commit 9abfb594260023d9f5e56859dd910415117be2b2 by Qt Cherry-pick Bot (on behalf of Christian Strømme) on 24/07/2026 at 17:23..
Make sure we mark the tree dirty when adding/removing an import-scene

The import scene injects itself into the layer's child list by setting
the dummy import-scene node's head and tail directly, deliberately
avoiding the normal add/remove path so the imported root's sibling
links and rootNodeRef aren't modified.

Mark the tree dirty explicitly in both setImportScene() and
removeImportScene() so the change triggers the needed reindex. On
removal we also reset the imported node's handle; we must not clear the
node's Imported state or rootNodeRef, as the node may be imported by
more than one view and neither is restored by the per-frame update.

The dummy import-scene node itself is added through addChild(), which
now front-inserts ImportScene nodes so the imported scene always gets
the lowest indices. That keeps a shared imported scene at the start
of a shared data store regardless of how many nodes a given view holds.
While here, simplify addChild()'s reparenting guard to only special-
case layer nodes.

Add tests covering the add/remove state transitions and the multi-view
sharing case.

Pick-to: 6.11
Change-Id: Ie1e5b063f7b64df06a26a57b074ba7b83d137dcf
Reviewed-by: Andy Nichols <[email protected]>
(cherry picked from commit 53c4de134c67fb3e468869acb325105ec0817b65)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>
https://invent.kde.org/qt/qt/qtquick3d/-/commit/9abfb594260023d9f5e56859dd910415117be2b2

Git commit 0dfa4e269cfa0be87fc823e74e6af4b62cb7c973 by Qt Cherry-pick Bot (on behalf of Christian Strømme) on 24/07/2026 at 17:23..
Remove uncommented code in refSceneManager

This code haven't been used since the initial commit, so just get rid of
it.

Pick-to: 6.11
Change-Id: Id1d07380d7b3127716f60189a0d19dadf03c9ae4
Reviewed-by: Andy Nichols <[email protected]>
(cherry picked from commit 7c2fcd2574ac33060bf3ace55ee2aa9a2733856e)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>
https://invent.kde.org/qt/qt/qtquick3d/-/commit/0dfa4e269cfa0be87fc823e74e6af4b62cb7c973