Add editable Deadlock Barrier Mesh ability geometry

- add Deadlock Barrier Mesh ability/widget with per-arm length controls
- persist arm lengths in JSON/Hive and include them in undo/redo history
- route geometry updates through providers and transition diffing
b6c26f8dd7Dara Adedeji committed on 3/9/2026, 10:55:47 PMparent313c20f
16 files changedLine totals unavailable