✨ feat(vscode): 新增「了解一块代码」：AI 找功能代码占一栏，对话里接着改

主栏标题栏的放大镜问要了解哪一块，占一个栏位建一栏（和收藏共用 30 个栏位，视图改名 slot1..30，按 slotKindN 分收藏 / 功能挂标题栏按钮），同时开对话页让 Claude 只读地在全部工作区文件夹里找，按 --json-schema 交回环节 → 文件 + 符号 + 一句话。
对话复用预览顶部的聊天（CodeQa.askTop：会话续接、进行中的一轮、记录存 workspaceState）；结构不合格算这一轮没答成、留着能再画出来。
条目每次画、点时按眼下的代码找：有语言插件的解析成代码块按「类名.方法名」找，没有的问 VS Code 文档符号；找不到画成灰的。

vscode/src/codeReader/features/featureLocate.test.ts

@@ -0,0 +1,109 @@
+import { describe, expect, it } from 'vitest'
+import { createBashAdapter } from '../languages/bash'
+import { createPythonAdapter } from '../languages/python'
+import { createRustAdapter } from '../languages/rust'
+import { createTypeScriptAdapter } from '../languages/typescript'
+import { runtime, WASM_DIR } from '../testSupport'
+import { locateInSource } from './featureLocate'
+
+const typescript = createTypeScriptAdapter(WASM_DIR)
+const python = createPythonAdapter(WASM_DIR)
+const rust = createRustAdapter(WASM_DIR)
+const bash = createBashAdapter(WASM_DIR)
+
+/** 找到的那块的名字在源码里是哪几个字、种类；找不到是 undefined */
+async function find(adapter: typeof typescript, languageId: string, source: string, symbol: string): Promise<{ text: string, kind: string } | undefined> {
+  const found = await locateInSource(runtime, adapter, languageId, source, symbol)
+  return found && { text: source.slice(found.range.startIndex, found.range.endIndex), kind: found.kind }
+}
+
+const TS = `
+import { api } from './api'
+
+export function login(name: string) {
+  return api.post('/login', { name })
+}
+
+export class AuthService {
+  private token = ''
+
+  async login(name: string) {
+    return login(name)
+  }
+
+  static create() {
+    return new AuthService()
+  }
+}
+
+export const LoginPage = () => {
+  const submit = () => login('a')
+  return submit
+}
+`
+
+const PY = `
+class UserService:
+    def renew(self, user):
+        return self._charge(user)
+
+    class Retry:
+        def schedule(self):
+            pass
+
+
+def renew_all():
+    pass
+`
+
+const RS = `
+pub struct Order;
+
+impl Order {
+    pub fn pay(&self) {}
+}
+
+fn main() {}
+`
+
+describe('按符号名在源码里找（语言插件解析出的块）', () => {
+  it('函数、类、组件按名字找；同名时取先出现的', async () => {
+    expect(await find(typescript, 'typescript', TS, 'login')).toEqual({ text: 'login', kind: 'function' })
+    expect(await find(typescript, 'typescript', TS, 'AuthService')).toEqual({ text: 'AuthService', kind: 'class' })
+    expect(await find(typescript, 'typescriptreact', TS, 'LoginPage')).toEqual({ text: 'LoginPage', kind: 'function' })
+  })
+
+  it('方法写成「类名.方法名」：先找类，再在里面找方法', async () => {
+    const found = await locateInSource(runtime, typescript, 'typescript', TS, 'AuthService.login')
+    expect(found?.kind).toBe('function')
+    // 是类里的那个 login，不是文件开头的函数
+    expect(found!.range.startIndex).toBeGreaterThan(TS.indexOf('class AuthService'))
+    expect(await find(typescript, 'typescript', TS, 'AuthService.create')).toEqual({ text: 'create', kind: 'function' })
+    expect(await find(typescript, 'typescript', TS, 'LoginPage.submit')).toEqual({ text: 'submit', kind: 'variable' })
+  })
+
+  it('类里的方法、嵌套类里的方法（Python）；impl 里的方法按类型名找（Rust）', async () => {
+    expect(await find(python, 'python', PY, 'UserService.renew')).toEqual({ text: 'renew', kind: 'function' })
+    expect(await find(python, 'python', PY, 'UserService.Retry.schedule')).toEqual({ text: 'schedule', kind: 'function' })
+    expect(await find(python, 'python', PY, 'renew_all')).toEqual({ text: 'renew_all', kind: 'function' })
+    expect(await find(rust, 'rust', RS, 'Order.pay')).toEqual({ text: 'pay', kind: 'function' })
+  })
+
+  it('类型（interface、type）和它们的成员按声明的名字找；shell 命令不算名字', async () => {
+    const types = 'export interface Favorite {\n  uri: string\n}\ntype Slot = number\n'
+    expect(await find(typescript, 'typescript', types, 'Favorite')).toEqual({ text: 'Favorite', kind: 'type' })
+    expect(await find(typescript, 'typescript', types, 'Favorite.uri')).toEqual({ text: 'uri', kind: 'field' })
+    expect(await find(typescript, 'typescript', types, 'Slot')).toEqual({ text: 'Slot', kind: 'type' })
+    expect(await find(rust, 'rust', 'pub type Id = u32;\n', 'Id')).toEqual({ text: 'Id', kind: 'statement' })
+    expect(await find(bash, 'shellscript', 'deploy() {\n  echo hi\n}\n', 'deploy')).toEqual({ text: 'deploy', kind: 'function' })
+    expect(await find(bash, 'shellscript', 'deploy() {\n  echo hi\n}\n', 'deploy.echo')).toBeUndefined()
+  })
+
+  it('找不到：没有这个名字、类里没有这个方法、写法不对', async () => {
+    expect(await find(typescript, 'typescript', TS, 'logout')).toBeUndefined()
+    expect(await find(typescript, 'typescript', TS, 'AuthService.logout')).toBeUndefined()
+    expect(await find(typescript, 'typescript', TS, 'Missing.login')).toBeUndefined()
+    expect(await find(typescript, 'typescript', TS, 'AuthService.')).toBeUndefined()
+    expect(await find(python, 'python', PY, 'UserService.schedule.renew')).toBeUndefined()
+  })
+})