fix(links): remove drag-end offset in straight/linear modes by honoring CENTER/NONE as no-offset (#5520)

- Add 'none' direction to path renderer
- Map CENTER/NONE to 'none' in adapter
- Keep start-end offset intentional; end follows cursor exactly
- Preserve spline behavior and arrow rendering

Verified with typecheck; no visual changes outside dragging behavior.

src/renderer/core/canvas/litegraph/litegraphLinkAdapter.ts

@@ -208,6 +208,9 @@ export class LitegraphLinkAdapter {
         return 'up'
       case LinkDirection.DOWN:
         return 'down'
+      case LinkDirection.CENTER:
+      case LinkDirection.NONE:
+        return 'none'
       default:
         return 'right'
     }

src/renderer/core/canvas/pathRenderer.ts

@@ -12,7 +12,7 @@ export interface Point {
   y: number
 }
 
-export type Direction = 'left' | 'right' | 'up' | 'down'
+export type Direction = 'left' | 'right' | 'up' | 'down' | 'none'
 export type RenderMode = 'spline' | 'straight' | 'linear'
 export type ArrowShape = 'triangle' | 'circle' | 'square'
 
@@ -255,6 +255,8 @@ export class CanvasPathRenderer {
       case 'down':
         innerA.y += l
         break
+      case 'none':
+        break
     }
 
     switch (endDir) {
@@ -270,6 +272,8 @@ export class CanvasPathRenderer {
       case 'down':
         innerB.y += l
         break
+      case 'none':
+        break
     }
 
     // Draw 4-point path: start -> innerA -> innerB -> end
@@ -306,6 +310,8 @@ export class CanvasPathRenderer {
       case 'down':
         innerA.y += l
         break
+      case 'none':
+        break
     }
 
     switch (endDir) {
@@ -321,6 +327,8 @@ export class CanvasPathRenderer {
       case 'down':
         innerB.y += l
         break
+      case 'none':
+        break
     }
 
     // Calculate midpoint using innerA/innerB positions (matching original)
@@ -399,6 +407,9 @@ export class CanvasPathRenderer {
         return { x: 0, y: -distance }
       case 'down':
         return { x: 0, y: distance }
+      case 'none':
+      default:
+        return { x: 0, y: 0 }
     }
   }
 
@@ -473,6 +484,8 @@ export class CanvasPathRenderer {
       case 'down':
         pa.y += dist * factor
         break
+      case 'none':
+        break
     }
 
     switch (endDirection) {
@@ -488,6 +501,8 @@ export class CanvasPathRenderer {
       case 'down':
         pb.y += dist * factor
         break
+      case 'none':
+        break
     }
 
     // Calculate bezier point (matching original computeConnectionPoint)
@@ -608,6 +623,9 @@ export class CanvasPathRenderer {
         return 'down'
       case 'down':
         return 'up'
+      case 'none':
+      default:
+        return 'none'
     }
   }