Implement drop-on-canvas + linkconnectoradapter consolidation (#5898)

Implements droponcanvas functionality and a linkconnectoradapter
refactor.

- Drop on canvas (Shift and default) integrated via LinkConnector
‘dropped-on-canvas’ with proper CanvasPointerEvent.
- LinkConnector adapter: now wraps the live canvas linkConnector (no
duplicate state); added dropOnCanvas() helper.
- Tests: Playwright scenarios for Shift-drop context menu/searchbox,
pinned endpoint, type prefilter, and post-selection auto-connect
(browser_tests/tests/vueNodes/interactions/links/linkInteraction.spec.ts).

There are some followup PRs that will fix/refactor some more noncritical
things, like the terrible slotid, the number/string nodeid confusion,
etc.

https://github.com/Comfy-Org/ComfyUI_frontend/pull/5780 (snapping) <--
https://github.com/Comfy-Org/ComfyUI_frontend/pull/5898 (drop on canvas
+ linkconnectoradapter refactor) <--
https://github.com/Comfy-Org/ComfyUI_frontend/pull/5903 (fix reroute
snapping)

---------

Co-authored-by: github-actions <github-actions@github.com>
Co-authored-by: Christian Byrne <cbyrne@comfy.org>
Co-authored-by: GitHub Action <action@github.com>

src/lib/litegraph/src/LGraphCanvas.ts

@@ -3319,7 +3319,15 @@ export class LGraphCanvas
 
                 if (slot && linkConnector.isInputValidDrop(node, slot)) {
                   highlightInput = slot
-                  highlightPos = node.getInputSlotPos(slot)
+                  if (LiteGraph.vueNodesMode) {
+                    const idx = node.inputs.indexOf(slot)
+                    highlightPos =
+                      idx !== -1
+                        ? getSlotPosition(node, idx, true)
+                        : node.getInputSlotPos(slot)
+                  } else {
+                    highlightPos = node.getInputSlotPos(slot)
+                  }
                   linkConnector.overWidget = overWidget
                 }
               }
@@ -3331,7 +3339,9 @@ export class LGraphCanvas
                   const result = node.findInputByType(firstLink.fromSlot.type)
                   if (result) {
                     highlightInput = result.slot
-                    highlightPos = node.getInputSlotPos(result.slot)
+                    highlightPos = LiteGraph.vueNodesMode
+                      ? getSlotPosition(node, result.index, true)
+                      : node.getInputSlotPos(result.slot)
                   }
                 } else if (
                   inputId != -1 &&
@@ -3356,7 +3366,9 @@ export class LGraphCanvas
               if (inputId === -1 && outputId === -1) {
                 const result = node.findOutputByType(firstLink.fromSlot.type)
                 if (result) {
-                  highlightPos = node.getOutputPos(result.index)
+                  highlightPos = LiteGraph.vueNodesMode
+                    ? getSlotPosition(node, result.index, false)
+                    : node.getOutputPos(result.index)
                 }
               } else {
                 // check if I have a slot below de mouse
@@ -5730,7 +5742,9 @@ export class LGraphCanvas
         if (!node) continue
 
         const startPos = firstReroute.pos
-        const endPos = node.getInputPos(link.target_slot)
+        const endPos: Point = LiteGraph.vueNodesMode
+          ? getSlotPosition(node, link.target_slot, true)
+          : node.getInputPos(link.target_slot)
         const endDirection = node.inputs[link.target_slot]?.dir
 
         firstReroute._dragging = true
@@ -5749,7 +5763,9 @@ export class LGraphCanvas
         const node = graph.getNodeById(link.origin_id)
         if (!node) continue
 
-        const startPos = node.getOutputPos(link.origin_slot)
+        const startPos: Point = LiteGraph.vueNodesMode
+          ? getSlotPosition(node, link.origin_slot, false)
+          : node.getOutputPos(link.origin_slot)
         const endPos = reroute.pos
         const startDirection = node.outputs[link.origin_slot]?.dir