feat(complexity): 新增 AUTO·由模型判断 复杂度档位 (tsk_zacmwH3chZpG)

新建任务时除手选 hard/medium/easy 外，新增 AUTO 档：先以 medium 落库
占位，建任务后异步用 sonnet 起一次轻量分类调用回填三档结果并记录理由，
不阻塞建任务返回；模型不可用/解析失败一律兜底 medium，绝不报错。

- web 看板：复杂度 seg 增加第四档 AUTO（默认选中，cyan 样式），提交 complexity='auto'
- src/api/server.ts：POST tasks 接受 'auto' → medium 占位 + 异步 classify 回填（可注入 classify 测试）
- src/executor/classify.ts（新增）：buildClassifyPrompt/parseClassification/classifyComplexity
  复用 cc.ts/models.ts，sonnet 省额度，无工具、限轮限时
- src/executor/models.ts：pickClassifierModel（复用 executor easy 档 + MAESTRO_MODEL_EASY 覆盖）
- src/store/store.ts：applyAutoComplexity 回填复杂度+重置状态+理由入产出字段+广播 task.updated
- test/classify.test.ts：解析映射/兜底、prompt、回填、建任务集成（13 例）

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/api/server.ts

@@ -7,6 +7,7 @@ import type { TaskStatus } from '../model/status.js';
 import type { Project, Autonomy } from '../model/types.js';
 import { syncProject, hasTodoJson } from '../sync/todo-sync.js';
 import { resolvedExecutorModels } from '../executor/models.js';
+import { classifyComplexity, type ClassifierFn } from '../executor/classify.js';
 import { mergeBranch } from '../executor/merge.js';
 import { git, removeWorktree } from '../executor/worktree.js';
 import { resolveLogo, LOGO_MIME } from './logo.js';
@@ -23,6 +24,8 @@ export interface ApiOptions {
   logger?: boolean;
   /** Claude 订阅额度查询（测试注入；默认直连 OAuth usage API，60s 缓存） */
   getUsage?: () => Promise<UsageInfo | null>;
+  /** AUTO 复杂度分类器（测试注入；默认 classifyComplexity，用 sonnet 起一次轻量调用） */
+  classify?: ClassifierFn;
 }
 
 /**
@@ -31,6 +34,7 @@ export interface ApiOptions {
  */
 export function buildServer(opts: ApiOptions): FastifyInstance {
   const { store } = opts;
+  const classify = opts.classify ?? ((title, description, cwd) => classifyComplexity(title, description, { cwd }));
   const app = Fastify({ logger: opts.logger ?? false });
 
   // Store 错误 → 400（业务校验），其余 → 500
@@ -152,13 +156,23 @@ export function buildServer(opts: ApiOptions): FastifyInstance {
     const { id } = req.params as { id: string };
     const b = req.body as Record<string, unknown>;
     if (!b?.title) throw new StoreError('title 必填');
-    if (!isComplexity(b.complexity)) throw new StoreError('complexity 必须是 hard|medium|easy');
-    return store.createTask({
-      projectId: id, title: String(b.title), complexity: b.complexity as Complexity,
+    // 'auto' = 由模型判定：先以 medium 落库占位，建任务后异步回填（不阻塞返回）
+    const auto = b.complexity === 'auto';
+    if (!auto && !isComplexity(b.complexity)) throw new StoreError('complexity 必须是 auto|hard|medium|easy');
+    const task = store.createTask({
+      projectId: id, title: String(b.title), complexity: auto ? 'medium' : (b.complexity as Complexity),
       parentId: b.parentId ? String(b.parentId) : null,
       priority: b.priority === undefined ? undefined : Number(b.priority),
       deps: Array.isArray(b.deps) ? (b.deps as string[]) : undefined,
     });
+    if (auto) {
+      // 异步分类回填：classifyComplexity 自身永不抛错（失败兜底 medium），外层再兜一层防御
+      const cwd = store.getProject(id)?.repoPath ?? process.cwd();
+      void classify(task.title, undefined, cwd)
+        .then(({ complexity, reason }) => store.applyAutoComplexity(task.id, complexity, reason))
+        .catch((e: unknown) => app.log.error(`任务 ${task.id} AUTO 复杂度分类失败（保留占位 medium）：${(e as Error).message}`));
+    }
+    return task;
   });
 
   app.get('/api/tasks/:id', (req) => {