[refactor] Migrate litegraph imports from npm package to local subtree

- Updated all imports from '@comfyorg/litegraph' to '@/lib/litegraph/src/'
- Replaced deep dist imports with direct source paths
- Updated CSS import in main.ts
- All imports now use the @ alias consistently

tests-ui/tests/litegraph.test.ts

@@ -1,6 +1,7 @@
-import { LGraph, LGraphNode, LiteGraph } from '@comfyorg/litegraph'
 import { describe, expect, it } from 'vitest'
 
+import { LGraph, LGraphNode, LiteGraph } from '@/lib/litegraph/src/litegraph'
+
 function swapNodes(nodes: LGraphNode[]) {
   const firstNode = nodes[0]
   const lastNode = nodes[nodes.length - 1]