fix(sdk): 超预算组丢最旧闭环+4xx丢弃计数（I1/M1）

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

sdk/test/transport.test.ts

@@ -110,20 +110,22 @@ describe("transport", () => {
     expect(fetchMock.mock.calls[1][1].body).toBe(fetchMock.mock.calls[0][1].body);
   });
 
-  it("400 不重试（参数错，重试无意义）", async () => {
+  it("400 不重试（参数错，重试无意义），事件落 dropped 桶（四桶对账无幽灵丢失）", async () => {
     fetchMock.mockResolvedValueOnce(res(400));
     const t = new Transport(mkCfg({ batchSize: 1 }));
     t.push({ event_id: "e1" });
     await vi.advanceTimersByTimeAsync(10000);
     expect(fetchMock).toHaveBeenCalledTimes(1);
+    expect(t.dropped).toBe(1); // M1：4xx 不重试但必须计丢弃
   });
 
-  it("403 不重试（权限错，重试只会掩盖配置问题）", async () => {
+  it("403 不重试（权限错，重试只会掩盖配置问题），事件落 dropped 桶", async () => {
     fetchMock.mockResolvedValueOnce(res(403));
     const t = new Transport(mkCfg({ batchSize: 1 }));
     t.push({ event_id: "e1" });
     await vi.advanceTimersByTimeAsync(10000);
     expect(fetchMock).toHaveBeenCalledTimes(1);
+    expect(t.dropped).toBe(1);
   });
 
   it("429 要重试（限流是暂态）", async () => {
@@ -313,7 +315,8 @@ describe("transport", () => {
       visitor_id: "v1",
       session_id: "s1",
       page_id: "p1",
-      properties: { blob: "x".repeat(65_000) }, // 信封+事件 > 60KB
+      // 须落在 (60_000, 64_000] 窗口：超信标预算触发降级，又不触发 fetch 64KB 裁剪守卫
+      properties: { blob: "x".repeat(62_000) },
     });
     t.flush(true);
     expect(beacon).not.toHaveBeenCalled(); // 超预算不走信标
@@ -405,6 +408,44 @@ describe("transport", () => {
       { event_id: "safe", visitor_id: "v1", session_id: "s1", page_id: "p1" },
     ]);
   });
+
+  // ---- I1/M1：超预算组送达闭环 + 4xx 丢弃计数 ----
+
+  it("超 64KB 组丢最旧闭环：裁剪至预算内送达，最旧事件计 dropped", () => {
+    const t = new Transport(mkCfg({ batchSize: 10 }));
+    const big = (id: string, n: number) => ({
+      event_id: id,
+      visitor_id: "v1",
+      session_id: "s1",
+      page_id: "p1",
+      properties: { blob: "x".repeat(n) },
+    });
+    t.push(big("e1", 33_000));
+    t.push(big("e2", 33_000));
+    t.push(big("e3", 2_000));
+    t.flush();
+    expect(fetchMock).toHaveBeenCalledTimes(1);
+    const body = JSON.parse(fetchMock.mock.calls[0][1].body);
+    expect(body.events.map((e: { event_id: string }) => e.event_id)).toEqual(["e2", "e3"]); // e1(最旧)被裁
+    expect(t.dropped).toBe(1); // 被裁的最旧事件逐条计 dropped
+  });
+
+  it("单事件超 64KB：整组裁空不发送不空转重试，全量计 dropped", async () => {
+    fetchMock.mockResolvedValue(res(500)); // 若误发送会进入重试空转——用调用数守卫
+    const t = new Transport(mkCfg({ batchSize: 10, maxRetry: 3 }));
+    t.push({
+      event_id: "huge",
+      visitor_id: "v1",
+      session_id: "s1",
+      page_id: "p1",
+      properties: { blob: "x".repeat(70_000) },
+    });
+    t.flush();
+    expect(fetchMock).not.toHaveBeenCalled(); // keepalive 64KiB 硬限确定性失败——不空转
+    await vi.advanceTimersByTimeAsync(60_000);
+    expect(fetchMock).not.toHaveBeenCalled();
+    expect(t.dropped).toBe(1); // 整组丢弃完毕
+  });
 });
 
 describe("mergeConfig", () => {