Color links as common type (#7211)

Previously the color of a link would simply use the type of the target
slot and fallback to the type of the origin slot. When a connection is
made to a node that accepts the any type ('*'), the link has the green
color of an unknown type.

Instead, when a connection is made, the type of a link is now calculated
as the greatest common type of the source and destination. This means
that connections to reroutes are correctly colored.

| Before | After |
| ------ | ----- |
| <img width="360" alt="before"
src="https://github.com/user-attachments/assets/a5544730-e69a-4c85-af33-b303bb30ae71"
/>| <img width="360" alt="after"
src="https://github.com/user-attachments/assets/7d7b59fd-1b79-440b-a97d-a1657313c484"
/>|

The code for calculating common types already exists, it has simply been
moved into litegraph and given a more descriptive name.

Resolves #7196

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7211-Color-links-as-common-type-2c16d73d365081188460f6b5973db962)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Alexander Brown <drjkl@comfy.org>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

src/lib/litegraph/src/LGraphNode.ts

@@ -10,6 +10,7 @@ import { useLayoutMutations } from '@/renderer/core/layout/operations/layoutMuta
 import { LayoutSource } from '@/renderer/core/layout/types'
 import { adjustColor } from '@/utils/colorUtil'
 import type { ColorAdjustOptions } from '@/utils/colorUtil'
+import { commonType, toClass } from '@/lib/litegraph/src/utils/type'
 
 import { SUBGRAPH_OUTPUT_ID } from '@/lib/litegraph/src/constants'
 import type { DragAndScale } from './DragAndScale'
@@ -84,7 +85,6 @@ import { findFreeSlotOfType } from './utils/collections'
 import { warnDeprecated } from './utils/feedback'
 import { distributeSpace } from './utils/spaceDistribution'
 import { truncateText } from './utils/textUtils'
-import { toClass } from './utils/type'
 import { BaseWidget } from './widgets/BaseWidget'
 import { toConcreteWidget } from './widgets/widgetMap'
 import type { WidgetTypeMap } from './widgets/widgetMap'
@@ -2832,9 +2832,12 @@ export class LGraphNode
       inputNode.disconnectInput(inputIndex, true)
     }
 
+    const maybeCommonType =
+      input.type && output.type && commonType(input.type, output.type)
+
     const link = new LLink(
       ++graph.state.lastLinkId,
-      input.type || output.type,
+      maybeCommonType || input.type || output.type,
       this.id,
       outputIndex,
       inputNode.id,