Support Right Click -> Save for animated webp (#6095)

Allow for Right Click -> Save Image to work for the "SaveAnimatedWEBP"
node.

Fixing this revealed other existing issues:
- Attempting to resize the node causes runaway scaling
- Right clicking on the image directly causes a browser context menu
without a save option.

Significant rewriting has been performed to resolve both of these
issues.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6095-Support-Right-Click-Save-for-animated-webp-28e6d73d3650818e85a2ec58c38c2aae)
by [Unito](https://www.unito.io)

src/scripts/ui/imagePreview.ts

@@ -1,3 +1,5 @@
+import type { LGraphNode } from '@/lib/litegraph/src/LGraphNode'
+
 import { app } from '../app'
 import { $el } from '../ui'
 
@@ -48,8 +50,8 @@ export function calculateImageGrid(
   return { cellWidth, cellHeight, cols, rows, shiftX }
 }
 
-// @ts-expect-error fixme ts strict error
-export function createImageHost(node) {
+/** @knipIgnoreUnusedButUsedByCustomNodes */
+export function createImageHost(node: LGraphNode) {
   const el = $el('div.comfy-img-preview')
   // @ts-expect-error fixme ts strict error
   let currentImgs
@@ -108,8 +110,8 @@ export function createImageHost(node) {
         }
         el.replaceChildren(...imgs)
         currentImgs = imgs
-        node.onResize(node.size)
-        node.graph.setDirtyCanvas(true, true)
+        node.onResize?.(node.size)
+        node.graph?.setDirtyCanvas(true, true)
       }
     },
     getHeight() {