Fix macro elements jumping to upper-left corner instead of being placed
at the correct drop position.
Root cause: The preview offset used itemsBoundingRect() (all items
including children), while Diagram::fromXml() computed its translation
offset from top-level items only. This mismatch caused fromXml to
translate elements to the wrong position.
Changes:
- Compute top-level-only bounding rect in dummy diagram constructor
to get the correct m_items_top_left reference point
- Pass final_pos + m_items_top_left to fromXml() so the internal
translation yields the intended final position
- Add braces around single-statement for-loop in fromXml
- Remove empty else block leftovers from debug cleanup
Kellermorph