[backport cloud/1.41] fix: prevent middle-click paste duplicating workflow on Linux (#10040)

Backport of #8259 to `cloud/1.41`

Automatically created by backport workflow.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10040-backport-cloud-1-41-fix-prevent-middle-click-paste-duplicating-workflow-on-Linux-3256d73d36508136884fd82505fb37d9)
by [Unito](https://www.unito.io)

Co-authored-by: Gregorius Bima Kharisma Wicaksana <51526537+bimakw@users.noreply.github.com>
Co-authored-by: bymyself <cbyrne@comfy.org>

src/lib/litegraph/src/LGraphCanvas.ts

@@ -1951,6 +1951,11 @@ export class LGraphCanvas implements CustomEventDispatcher<LGraphCanvasEventMap>
     return false
   }
 
+  /** Prevents default for middle-click auxclick only. */
+  _preventMiddleAuxClick(e: MouseEvent): void {
+    if (e.button === 1) e.preventDefault()
+  }
+
   /** Captures an event and prevents default - returns true. */
   _doReturnTrue(e: Event): boolean {
     e.preventDefault()
@@ -1986,6 +1991,8 @@ export class LGraphCanvas implements CustomEventDispatcher<LGraphCanvasEventMap>
     canvas.addEventListener('pointercancel', this._mousecancel_callback, true)
 
     canvas.addEventListener('contextmenu', this._doNothing)
+    // Prevent middle-click paste (PRIMARY clipboard on Linux) - fixes #4464
+    canvas.addEventListener('auxclick', this._preventMiddleAuxClick)
 
     // Keyboard
     this._key_callback = this.processKey.bind(this)
@@ -2024,6 +2031,7 @@ export class LGraphCanvas implements CustomEventDispatcher<LGraphCanvasEventMap>
     canvas.removeEventListener('keydown', this._key_callback!)
     document.removeEventListener('keyup', this._key_callback!)
     canvas.removeEventListener('contextmenu', this._doNothing)
+    canvas.removeEventListener('auxclick', this._preventMiddleAuxClick)
     canvas.removeEventListener('dragenter', this._doReturnTrue)
 
     this._mousedown_callback = undefined