Adds ElkEdgeVerticalClearance.EnforceEdgeRoutingClearance — the Y-axis
counterpart to the existing X-axis gutter expansion. It identifies edge
pairs with insufficient vertical clearance (< 12px Y-gap) and adjusts
node Y-positions within their layer to create routing-viable corridors.
Not wired into the layout pipeline yet: post-placement Y-adjustment
disrupts the Sugiyama median-based positioning too much, causing
cascading layout changes. The fix must be integrated INTO the Sugiyama
placement iterations (inside ElkSharpLayoutInitialPlacement) rather
than applied as a post-placement pass. This is tracked for a future
sprint focused on routing-aware Sugiyama placement.
Root cause analysis confirms all remaining violations (3 gateway hooks,
1 target join, 1 shared lane, 3 under-node) are caused by Y-gaps of
5px, 8px, and 22px between connected nodes — too narrow for clean
orthogonal edge routing.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
