⚡ perf(vscode): 代码阅读预览发给页面的块只记相对位置：块在源码里占的地方记成离前一块多远、自己多长，块里名字的下标从块的开头算，页面从文件开头累加回文件里的位置、和扩展端打交道的地方都在一处换算；靠前改了代码，后面内容没变的块发过去一模一样，扩展端自己的块和发给页面的块分成两种类型

vscode/webview-ui/src/codeReader/App.test.tsx

@@ -7,6 +7,7 @@ import { act } from 'react'
 import { createRoot } from 'react-dom/client'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { App } from './App'
+import { NO_SPAN } from './testBlocks'
 import { createViewStateStore } from './viewState'
 
 /**
@@ -118,8 +119,7 @@ function block(id: string, anchor: string): BlockView {
     anchor,
     kind: 'function',
     callTree: {},
-    startLine: 0,
-    endLine: 1,
+    span: NO_SPAN,
     attributes: { kind: 'function' },
     concepts: [{ id: 'function', label: 'function', icon: 'braces' }],
     children: [],