Fix disconnection of subgraphInput links (#6258)

`LLink.disconnect` is intended to cleanup only the link itself. #4800
mistakenly assumed that it would perform all required steps for
disconnection. Later, #5015 would partially resolve this by adding some
of the missing functionality into `LLink.disconnect`, but this still
left output cleanup unhandled and failed to call
`node.onConnectionsChanged`.

This PR instead moves the disconnection code to call the function that
already has robust handling for these items and removes the
no-longer-needed and potentially misleading workaround.

Resolves #6247

Also un-skipped several SubgraphIO tests. They appear to function fine.
I'm assuming the reasons for them being skipped have been resolved.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6258-Fix-disconnection-of-subgraphInput-links-2966d73d36508112ad1fe602cdcf461b)
by [Unito](https://www.unito.io)

tests-ui/tests/litegraph/core/LLink.test.ts

@@ -1,6 +1,6 @@
-import { describe, expect, it, vi } from 'vitest'
+import { describe, expect } from 'vitest'
 
-import { LGraph, LGraphNode, LLink } from '@/lib/litegraph/src/litegraph'
+import { LLink } from '@/lib/litegraph/src/litegraph'
 
 import { test } from './fixtures/testExtensions'
 
@@ -14,84 +14,4 @@ describe('LLink', () => {
     const link = new LLink(1, 'float', 4, 2, 5, 3)
     expect(link.serialize()).toMatchSnapshot('Basic')
   })
-
-  describe('disconnect', () => {
-    it('should clear the target input link reference when disconnecting', () => {
-      // Create a graph and nodes
-      const graph = new LGraph()
-      const sourceNode = new LGraphNode('Source')
-      const targetNode = new LGraphNode('Target')
-
-      // Add nodes to graph
-      graph.add(sourceNode)
-      graph.add(targetNode)
-
-      // Add slots
-      sourceNode.addOutput('out', 'number')
-      targetNode.addInput('in', 'number')
-
-      // Connect the nodes
-      const link = sourceNode.connect(0, targetNode, 0)
-      expect(link).toBeDefined()
-      expect(targetNode.inputs[0].link).toBe(link?.id)
-
-      // Mock setDirtyCanvas
-      const setDirtyCanvasSpy = vi.spyOn(targetNode, 'setDirtyCanvas')
-
-      // Disconnect the link
-      link?.disconnect(graph)
-
-      // Verify the target input's link reference is cleared
-      expect(targetNode.inputs[0].link).toBeNull()
-
-      // Verify setDirtyCanvas was called
-      expect(setDirtyCanvasSpy).toHaveBeenCalledWith(true, false)
-    })
-
-    it('should handle disconnecting when target node is not found', () => {
-      // Create a link with invalid target
-      const graph = new LGraph()
-      const link = new LLink(1, 'number', 1, 0, 999, 0) // Invalid target id
-
-      // Should not throw when disconnecting
-      expect(() => link.disconnect(graph)).not.toThrow()
-    })
-
-    it('should only clear link reference if it matches the current link id', () => {
-      // Create a graph and nodes
-      const graph = new LGraph()
-      const sourceNode1 = new LGraphNode('Source1')
-      const sourceNode2 = new LGraphNode('Source2')
-      const targetNode = new LGraphNode('Target')
-
-      // Add nodes to graph
-      graph.add(sourceNode1)
-      graph.add(sourceNode2)
-      graph.add(targetNode)
-
-      // Add slots
-      sourceNode1.addOutput('out', 'number')
-      sourceNode2.addOutput('out', 'number')
-      targetNode.addInput('in', 'number')
-
-      // Create first connection
-      const link1 = sourceNode1.connect(0, targetNode, 0)
-      expect(link1).toBeDefined()
-
-      // Disconnect first connection
-      targetNode.disconnectInput(0)
-
-      // Create second connection
-      const link2 = sourceNode2.connect(0, targetNode, 0)
-      expect(link2).toBeDefined()
-      expect(targetNode.inputs[0].link).toBe(link2?.id)
-
-      // Try to disconnect the first link (which is already disconnected)
-      // It should not affect the current connection
-      link1?.disconnect(graph)
-
-      // The input should still have the second link
-      expect(targetNode.inputs[0].link).toBe(link2?.id)
-    })
-  })
 })