feat(usage): 用量明细——/api/usage 加 week 窗口+runs 计数，新增 /api/usage/detail

costSummary 顶层补 runs 计数、period 扩 day|week|month；新增 usageDetail(day|week|month) 返回时间序列分桶 + 分项目下钻（token/花费/任务数/模型，model 维度沿用 usage JSON 近似口径）。

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

src/api/server.ts

@@ -196,12 +196,19 @@ export function buildServer(opts: ApiOptions): FastifyInstance {
   // ?period=day|month（默认 month）；?project=<id> 限定单项目成本。
   app.get('/api/usage', async (req) => {
     const q = req.query as { period?: string; project?: string };
-    const period = q.period === 'day' ? 'day' : 'month';
+    const period = q.period === 'day' ? 'day' : q.period === 'week' ? 'week' : 'month';
     const quota = await getUsage();
     const cost = store.costSummary(period, q.project && q.project.trim() ? q.project.trim() : undefined);
     return { ...(quota ?? {}), cost };
   });
 
+  // 用量详情：时间序列（按天/按月）+ 分项目下钻，供侧栏「详情」弹框。
+  app.get('/api/usage/detail', (req) => {
+    const q = req.query as { granularity?: string };
+    const granularity = q.granularity === 'month' ? 'month' : q.granularity === 'week' ? 'week' : 'day';
+    return store.usageDetail(granularity);
+  });
+
   // 健康检查：daemon 存活 + DB 可读 + 在途 run 数。
   app.get('/api/health', () => {
     let db = true;