feat(health-check): replace real-LLM probe with HTTP reachability check

The provider panel health check sent a real streaming model request, which many third-party providers block (401/403/WAF), causing false negatives while only stable official endpoints passed. Replace it with a lightweight reachability probe: GET the provider base_url and treat any HTTP response (200/4xx/5xx) as reachable; only DNS/connect/TLS/timeout count as failure. Latency is the probe's TTFB.

Backend (services/stream_check.rs): rewrite ~2200 -> ~350 lines, dropping real-request building, format conversion, auth and API-path resolution while keeping per-app base_url extraction. Defaults: 8s timeout, 1 retry, 1500ms degraded threshold.

Failover invariant: the reachability check must never reset the circuit breaker (reachable != usable; a 403 host is reachable but broken for real traffic). Remove the resetCircuitBreaker call from useStreamCheck; failover failure detection stays driven solely by real proxy traffic (forwarder/circuit_breaker untouched). useResetCircuitBreaker is kept dormant for a future manual-recovery entry.

Open the check to all providers: drop the official/copilot/codex-oauth/third-party gating and the 'sends a real request' confirm dialog. For official providers whose base_url is intentionally empty, fall back to the endpoint the client actually uses (Claude -> api.anthropic.com, Codex -> chatgpt.com/backend-api/codex, Gemini -> generativelanguage). Non-official providers with a missing base_url still error to avoid a false green light. Claude Desktop Official is native 1P mode (talks to claude.ai, cc-switch not in the request path, no reliable endpoint) so its button stays hidden.

Slim StreamCheckConfig and per-provider testConfig to timeout/threshold/retries (drop test model + prompt); sync zh/en/ja/zh-TW. Retain the now-unused anthropic_to_openai/anthropic_to_gemini transform utilities and their test suites.

src/hooks/useStreamCheck.ts

@@ -6,12 +6,17 @@ import {
   type StreamCheckResult,
 } from "@/lib/api/model-test";
 import type { AppId } from "@/lib/api";
-import { useResetCircuitBreaker } from "@/lib/query/failover";
 
+/**
+ * 供应商连通性检查。
+ *
+ * 只探测 base_url 是否可达（任何 HTTP 响应都算可达），不发真实大模型请求。
+ * 刻意 **不** 重置故障转移熔断器——可达 ≠ 配置正确，一个端口通但鉴权废的供应商
+ * 不应被误判为"健康"而切回线上。熔断器只由真实转发流量驱动（见 proxy/forwarder.rs）。
+ */
 export function useStreamCheck(appId: AppId) {
   const { t } = useTranslation();
   const [checkingIds, setCheckingIds] = useState<Set<string>>(new Set());
-  const resetCircuitBreaker = useResetCircuitBreaker();
 
   const checkProvider = useCallback(
     async (
@@ -25,89 +30,38 @@ export function useStreamCheck(appId: AppId) {
 
         if (result.status === "operational") {
           toast.success(
-            t("streamCheck.operational", {
+            t("streamCheck.reachable", {
               providerName: providerName,
               responseTimeMs: result.responseTimeMs,
-              defaultValue: `${providerName} 运行正常 (${result.responseTimeMs}ms)`,
+              defaultValue: `${providerName} 连通正常 (${result.responseTimeMs}ms)`,
             }),
             { closeButton: true },
           );
-
-          // 测试通过后重置熔断器状态
-          resetCircuitBreaker.mutate({ providerId, appType: appId });
         } else if (result.status === "degraded") {
           toast.warning(
-            t("streamCheck.degraded", {
+            t("streamCheck.reachableSlow", {
               providerName: providerName,
               responseTimeMs: result.responseTimeMs,
-              defaultValue: `${providerName} 响应较慢 (${result.responseTimeMs}ms)`,
+              defaultValue: `${providerName} 连通但较慢 (${result.responseTimeMs}ms)`,
             }),
           );
-
-          // 降级状态也重置熔断器，因为至少能通信
-          resetCircuitBreaker.mutate({ providerId, appType: appId });
-        } else if (result.errorCategory === "modelNotFound") {
-          // 专门处理"模型不存在/已下架"：指向配置入口，比通用 404 文案更有指导性
-          toast.error(
-            t("streamCheck.modelNotFound", {
-              providerName: providerName,
-              model: result.modelUsed,
-              defaultValue: `${providerName} 测试模型 ${result.modelUsed} 不存在或已下架`,
-            }),
-            {
-              description: t("streamCheck.modelNotFoundHint", {
-                defaultValue: "",
-              }),
-              duration: 10000,
-              closeButton: true,
-            },
-          );
-        } else if (result.errorCategory === "quotaExceeded") {
-          toast.warning(
-            t("streamCheck.quotaExceeded", {
-              providerName: providerName,
-              defaultValue: `${providerName} Coding Plan quota has been exceeded`,
-            }),
-            {
-              description: t("streamCheck.quotaExceededHint", {
-                defaultValue: "",
-              }),
-              duration: 10000,
-              closeButton: true,
-            },
-          );
         } else {
-          const httpStatus = result.httpStatus;
-          const hintKey = httpStatus
-            ? `streamCheck.httpHint.${httpStatus >= 500 ? "5xx" : httpStatus}`
-            : null;
-          const description =
-            (hintKey ? t(hintKey, { defaultValue: "" }) : "") || undefined;
-
-          // 401/403/400 = 检查被拒（供应商可能正常）；429/5xx = 临时问题
-          const isProbeRejection =
-            httpStatus != null &&
-            ([401, 403, 400, 429].includes(httpStatus) || httpStatus >= 500);
-
-          if (isProbeRejection) {
-            toast.warning(
-              t("streamCheck.rejected", {
-                providerName: providerName,
-                message: result.message,
-                defaultValue: `${providerName} 检查被拒: ${result.message}`,
+          // 仅当无法建立连接（DNS / 连接被拒 / TLS / 超时）才会到这里
+          toast.error(
+            t("streamCheck.unreachable", {
+              providerName: providerName,
+              message: result.message,
+              defaultValue: `${providerName} 无法连通: ${result.message}`,
+            }),
+            {
+              description: t("streamCheck.unreachableHint", {
+                defaultValue:
+                  "无法建立连接（DNS / 连接 / TLS / 超时）。请检查 base_url 与网络。",
               }),
-              { description, duration: 8000, closeButton: true },
-            );
-          } else {
-            toast.error(
-              t("streamCheck.failed", {
-                providerName: providerName,
-                message: result.message,
-                defaultValue: `${providerName} 检查失败: ${result.message}`,
-              }),
-              { description, duration: 8000, closeButton: true },
-            );
-          }
+              duration: 8000,
+              closeButton: true,
+            },
+          );
         }
 
         return result;
@@ -128,7 +82,7 @@ export function useStreamCheck(appId: AppId) {
         });
       }
     },
-    [appId, t, resetCircuitBreaker],
+    [appId, t],
   );
 
   const isChecking = useCallback(