fix(chv-muse-r12fix-4): detect_checkout 接进 CDP broker（P10）

R12 真机：detect_checkout 在 chv-guest/、host.py、
executor.py 里零引用，结账页无任何拦截。按 P10 gap §4.1
接线：broker 加载 cloud/chv/checkout_detect.py（同目录
优先，仓库路径兜底；缺失时降级关闭检测、写警告，绝不
crash-loop）；snapshot() 每次重算 verdict（aria 行拼伪节点，
与 _form_risk 同形），open() 导航前后两道门——落点是结账
页时返回 form_submit ask 并暂停，上一页是结账页时下一次
导航先审批；ask 批过后同 URL 不再重复 ask（批准即放行，
与 form_risk 同口径）；verdict 进 snapshot()/status() 回包。
build.sh：checkout_detect.py 条件拷入 /usr/local/bin/（0644，
P3/P6 同款只警告口径，M4 不硬要求 cloud/），
extra_contents 与两处 lockfile 登记补齐。钱包三腿不在本轮
范围，未动。

cloud/tests/test_chv_muse_p4.py

@@ -462,6 +462,58 @@ class CdpBrokerTest(unittest.TestCase):
             third = broker.open("https://example.com/other")
             self.assertTrue(third["ok"], third)
 
+    def test_checkout_open_returns_ask_and_pauses(self):
+        # round-12 修复轮（项 4，P10）：落点是结账页时，open
+        # 导航返回 ask 并暂停（P10 gap §4.1）。
+        aria = ("- generic [ref=e1]:\n"
+                "  - heading \"Checkout\" [ref=e2]\n"
+                "  - button \"Pay now\" [ref=e3]\n"
+                "  - text \"Total: $49.99\" [ref=e4]")
+        with tempfile.TemporaryDirectory() as tmp:
+            broker, page, _f = _make_broker(tmp, aria=aria)
+            first = broker.open("https://shop.example.com/checkout")
+            self.assertFalse(first["ok"])
+            self.assertTrue(first.get("ask"))
+            self.assertIn("ask_id", first)
+            self.assertEqual(len(page.goto_calls), 1)
+            self.assertTrue(broker.status()["paused"])
+            asks = broker.list_asks()["asks"]
+            self.assertEqual(len(asks), 1)
+            self.assertEqual(asks[0]["kind"], "form_submit")
+            self.assertIn("结账页命中", asks[0]["detail"])
+
+    def test_checkout_allowed_then_open_ok(self):
+        # 批过 ask 后同 URL 再 open 不再重复 ask（与 form_risk
+        #“批准即放行”同口径）；但随后导航到别的 URL 时，上一页
+        # 仍是结账页，导航前门再次拦下。
+        aria = ("- generic [ref=e1]:\n"
+                "  - heading \"Checkout\" [ref=e2]\n"
+                "  - button \"Pay now\" [ref=e3]\n"
+                "  - text \"Total: $49.99\" [ref=e4]")
+        with tempfile.TemporaryDirectory() as tmp:
+            broker, page, _f = _make_broker(tmp, aria=aria)
+            first = broker.open("https://shop.example.com/checkout")
+            self.assertTrue(first.get("ask"))
+            asks = broker.list_asks()["asks"]
+            ok = broker.resolve_ask(asks[0]["ask_id"], "allowed")
+            self.assertTrue(ok["ok"])
+            second = broker.open("https://shop.example.com/checkout")
+            self.assertTrue(second["ok"], second)
+            self.assertTrue(second["checkout"]["is_checkout"])
+            self.assertEqual(second["checkout"]["confidence"], "high")
+            self.assertFalse(broker.status()["paused"])
+            third = broker.open("https://example.com/other")
+            self.assertFalse(third["ok"])
+            self.assertTrue(third.get("ask"))
+            self.assertEqual(len(page.goto_calls), 2)
+
+    def test_non_checkout_open_ok(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            broker, _page, _f = _make_broker(tmp)
+            resp = broker.open("https://example.com")
+            self.assertTrue(resp["ok"], resp)
+            self.assertFalse(resp["checkout"]["is_checkout"])
+
     def test_post_navigation_request_auto_pauses(self):
         with tempfile.TemporaryDirectory() as tmp:
             broker, page, _f = _make_broker(tmp)
@@ -820,6 +872,12 @@ class BuildDryRunTest(unittest.TestCase):
                 dest = os.path.join(repo, rel)
                 os.makedirs(os.path.dirname(dest), exist_ok=True)
                 shutil.copy2(ROOT / rel, dest)
+            # round-12 修复轮（项 4，P10）：checkout_detect 是
+            # cloud/ 下的条件拷入件，夹具须一并拷入才走拷入分支。
+            rel = "cloud/chv/checkout_detect.py"
+            dest = os.path.join(repo, rel)
+            os.makedirs(os.path.dirname(dest), exist_ok=True)
+            shutil.copy2(ROOT / rel, dest)
             codex = os.path.join(bindir, "codex")
             with open(codex, "w") as fh:
                 fh.write("#!/bin/sh\necho 'codex-cli 0.164.0-alpha.9'\n")
@@ -862,7 +920,10 @@ class BuildDryRunTest(unittest.TestCase):
                            # 三件进镜像，干跑输出须含拷入与 enable。
                            "chv-gitea-worker",
                            "chv-gitea-worker.service",
-                           "systemctl enable chv-gitea-worker"):
+                           "systemctl enable chv-gitea-worker",
+                           # round-12 修复轮（项 4，P10）：结账检测
+                           # 模块进镜像，干跑输出须含条件拷入行。
+                           "checkout_detect"):
                 self.assertIn(needle, out, needle)
             # P1 文件不在本分支：干跑只警告、不失败。
             self.assertIn("vsock_notify.py 不在仓库里", out)