fix(security): 凭证扫描放行依赖注入传参 + 四仓口径更正

`api_key=volcengine.api_key` 这类**依赖注入传参**被 KEY-ASSIGN 判为疑似凭证。
这是规则的真缺口而非代码问题：行里没有任何秘密，而做 DI 的代码到处都是这种
写法——绕过一次就得在每个调用点绕过，那等于把规则废掉。故改规则。

新增 ALLOW_REFERENCE，刻意收得很紧以免开后门：
- 值必须是**未加引号**的小写起首标识符引用（真密钥要么带引号，要么不是标识符形状）
- 只允许**恰好一个点且随即行尾**
- 连字符不在字符集内

对抗性夹具验证（三真三假）：
- 拦下 `api_key = "sk-T3Blbk…"`（OpenAI 形态）
- 拦下 `secret_key: "AKID…"`（腾讯云形态）
- 拦下 `auth_token=eyJ….eyJ….Sfl…`（**三段式 JWT——两个点，故不落进放行**）
- 放行 `api_key=lowercase.reference` / `api_key = settings.api_key` / `api_token: config.authToken`
原 5 形态泄漏夹具复验仍 8 条命中，一条不少。

另更正口径：脚本头与 git-workflow.md 仍写「三仓同构」，实际已是四仓——
patbond-ai 是唯一持有 AI 服务商凭证的仓，漏同步它风险最大。四仓 md5 已一致
（4945940093b4b8413b7d3eec8bf6a5ec），四仓 --all 全绿。

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/providers/volcengine/test_client.py

@@ -0,0 +1,153 @@
+"""`ArkClient` 的测试——只测传输层：鉴权头、错误解包、连接生命周期。
+
+**刻意不测任何视频业务**：本 client 不认识「视频」，测试也不该。视频相关的断言
+在 `test_video.py`。
+"""
+
+from __future__ import annotations
+
+import httpx
+import pytest
+
+from app.domain.generation import Retry, UserFacing
+from app.providers.volcengine.client import ArkClient, ArkError
+
+#: 显式的假值。防泄漏扫描会拦下 `api_key = "..."` 形态（规则正确——这正是真实
+#: 密钥最常见的泄漏形态），故夹具用 ALLOW 清单认可的占位词。
+FAKE_API_KEY = "dummy-api-key-for-tests"
+
+BASE_URL = "https://ark.example.invalid/api/v3"
+
+
+def client_with(handler) -> ArkClient:
+    return ArkClient(
+        api_key=FAKE_API_KEY,
+        base_url=BASE_URL,
+        client=httpx.Client(transport=httpx.MockTransport(handler)),
+    )
+
+
+class TestConstruction:
+    def test_missing_api_key_fails_at_construction_not_at_first_call(self):
+        # 缺密钥是配置错误。让它表现为一串莫名的 401 会浪费排查时间。
+        with pytest.raises(ValueError, match="ARK_API_KEY"):
+            ArkClient(api_key="", base_url=BASE_URL)
+
+    def test_trailing_slash_in_base_url_does_not_double_up(self):
+        def handler(request: httpx.Request) -> httpx.Response:
+            assert "//contents" not in str(request.url)
+            return httpx.Response(200, json={})
+
+        ArkClient(
+            api_key=FAKE_API_KEY,
+            base_url=BASE_URL + "/",
+            client=httpx.Client(transport=httpx.MockTransport(handler)),
+        ).get("/contents/x")
+
+
+class TestAuthAndTransport:
+    def test_bearer_token_and_content_type_are_sent(self):
+        def handler(request: httpx.Request) -> httpx.Response:
+            assert request.headers["Authorization"] == f"Bearer {FAKE_API_KEY}"
+            assert request.headers["Content-Type"] == "application/json"
+            return httpx.Response(200, json={"ok": True})
+
+        assert client_with(handler).post("/x", {}) == {"ok": True}
+
+    def test_get_and_post_hit_the_expected_method(self):
+        seen: list[str] = []
+
+        def handler(request: httpx.Request) -> httpx.Response:
+            seen.append(request.method)
+            return httpx.Response(200, json={})
+
+        client = client_with(handler)
+        client.post("/x", {})
+        client.get("/x")
+        assert seen == ["POST", "GET"]
+
+    def test_network_failure_is_classified_retryable(self):
+        def handler(request):
+            raise httpx.ConnectError("connection refused")
+
+        with pytest.raises(ArkError) as exc:
+            client_with(handler).get("/x")
+        assert exc.value.failure.retry is Retry.BACKOFF
+        assert exc.value.http_status is None
+
+
+class TestErrorUnwrapping:
+    def test_vendor_error_body_is_classified(self):
+        def handler(request):
+            return httpx.Response(
+                429,
+                json={
+                    "error": {
+                        "code": "RateLimitExceeded.EndpointRPMExceeded",
+                        "message": "RPM limit exceeded",
+                    }
+                },
+            )
+
+        with pytest.raises(ArkError) as exc:
+            client_with(handler).get("/x")
+        assert exc.value.failure.retry is Retry.BACKOFF
+        assert exc.value.failure.user_facing is UserFacing.RATE_LIMITED
+        assert (
+            exc.value.failure.provider_code == "RateLimitExceeded.EndpointRPMExceeded"
+        )
+        assert exc.value.http_status == 429
+
+    def test_vendor_message_is_preserved_for_troubleshooting(self):
+        def handler(request):
+            return httpx.Response(
+                401,
+                json={
+                    "error": {"code": "AuthenticationError", "message": "key invalid"}
+                },
+            )
+
+        with pytest.raises(ArkError) as exc:
+            client_with(handler).get("/x")
+        assert "key invalid" in exc.value.failure.message
+
+    def test_non_json_error_body_is_not_swallowed(self):
+        # 打到错误地址时常见：网关返回 HTML 错误页。静默会让排查绕远路。
+        def handler(request):
+            return httpx.Response(502, text="<html>bad gateway</html>")
+
+        with pytest.raises(ArkError) as exc:
+            client_with(handler).get("/x")
+        assert "bad gateway" in exc.value.failure.message
+        assert exc.value.failure.retry is Retry.BACKOFF
+
+    def test_non_json_success_body_is_an_error_too(self):
+        def handler(request):
+            return httpx.Response(200, text="not json")
+
+        with pytest.raises(ArkError, match="不是合法 JSON"):
+            client_with(handler).get("/x")
+
+
+class TestConnectionOwnership:
+    def test_injected_client_is_not_closed_by_us(self):
+        """注入进来的连接池归调用方管理。
+
+        在这里关掉会让共享同一个 httpx.Client 的其他适配器一起失效——接了第二个
+        火山接口后这会变成一个极难查的偶发失败。
+        """
+        injected = httpx.Client(
+            transport=httpx.MockTransport(lambda r: httpx.Response(200, json={}))
+        )
+        ArkClient(api_key=FAKE_API_KEY, base_url=BASE_URL, client=injected).close()
+        assert not injected.is_closed
+
+    def test_own_client_is_closed(self):
+        client = ArkClient(api_key=FAKE_API_KEY, base_url=BASE_URL)
+        client.close()
+        assert client._client.is_closed
+
+    def test_usable_as_context_manager(self):
+        with ArkClient(api_key=FAKE_API_KEY, base_url=BASE_URL) as client:
+            inner = client._client
+        assert inner.is_closed