Restore accidentally removed ARROW_LENGTH constant in CoordinateSystemNode When the view-layer clamping code was deleted (moving origin bounds enforcement to the model layer), the ARROW_LENGTH = 120 constant was inadvertently removed along with it. This caused five TS2304 "Cannot find name 'ARROW_LENGTH'" type errors that were not present before the code-review fixes. https://claude.ai/code/session_0166NkhC8JkCQWkiRvir4o2B - #16