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/components/providers/forms/ProviderAdvancedConfig.tsx

@@ -61,7 +61,7 @@ export function ProviderAdvancedConfig({
             <FlaskConical className="h-4 w-4 text-muted-foreground" />
             <span className="font-medium">
               {t("providerAdvanced.testConfig", {
-                defaultValue: "模型测试配置",
+                defaultValue: "连通检测配置",
               })}
             </span>
           </div>
@@ -106,31 +106,10 @@ export function ProviderAdvancedConfig({
             <p className="text-sm text-muted-foreground">
               {t("providerAdvanced.testConfigDesc", {
                 defaultValue:
-                  "为此供应商配置单独的模型测试参数，不启用时使用全局配置。",
+                  "为此供应商配置单独的连通检测参数（超时/阈值/重试），不启用时使用全局配置。",
               })}
             </p>
             <div className="grid grid-cols-1 md:grid-cols-2 gap-4">
-              <div className="space-y-2">
-                <Label htmlFor="test-model">
-                  {t("providerAdvanced.testModel", {
-                    defaultValue: "测试模型",
-                  })}
-                </Label>
-                <Input
-                  id="test-model"
-                  value={testConfig.testModel || ""}
-                  onChange={(e) =>
-                    onTestConfigChange({
-                      ...testConfig,
-                      testModel: e.target.value || undefined,
-                    })
-                  }
-                  placeholder={t("providerAdvanced.testModelPlaceholder", {
-                    defaultValue: "留空使用全局配置",
-                  })}
-                  disabled={!testConfig.enabled}
-                />
-              </div>
               <div className="space-y-2">
                 <Label htmlFor="test-timeout">
                   {t("providerAdvanced.timeoutSecs", {
@@ -141,7 +120,7 @@ export function ProviderAdvancedConfig({
                   id="test-timeout"
                   type="number"
                   min={1}
-                  max={300}
+                  max={60}
                   value={testConfig.timeoutSecs || ""}
                   onChange={(e) =>
                     onTestConfigChange({
@@ -151,26 +130,7 @@ export function ProviderAdvancedConfig({
                         : undefined,
                     })
                   }
-                  placeholder="45"
-                  disabled={!testConfig.enabled}
-                />
-              </div>
-              <div className="space-y-2">
-                <Label htmlFor="test-prompt">
-                  {t("providerAdvanced.testPrompt", {
-                    defaultValue: "测试提示词",
-                  })}
-                </Label>
-                <Input
-                  id="test-prompt"
-                  value={testConfig.testPrompt || ""}
-                  onChange={(e) =>
-                    onTestConfigChange({
-                      ...testConfig,
-                      testPrompt: e.target.value || undefined,
-                    })
-                  }
-                  placeholder="Who are you?"
+                  placeholder="8"
                   disabled={!testConfig.enabled}
                 />
               </div>
@@ -184,7 +144,7 @@ export function ProviderAdvancedConfig({
                   id="degraded-threshold"
                   type="number"
                   min={100}
-                  max={60000}
+                  max={10000}
                   value={testConfig.degradedThresholdMs || ""}
                   onChange={(e) =>
                     onTestConfigChange({
@@ -194,7 +154,7 @@ export function ProviderAdvancedConfig({
                         : undefined,
                     })
                   }
-                  placeholder="6000"
+                  placeholder="1500"
                   disabled={!testConfig.enabled}
                 />
               </div>
@@ -208,7 +168,7 @@ export function ProviderAdvancedConfig({
                   id="max-retries"
                   type="number"
                   min={0}
-                  max={10}
+                  max={5}
                   value={testConfig.maxRetries ?? ""}
                   onChange={(e) =>
                     onTestConfigChange({
@@ -218,7 +178,7 @@ export function ProviderAdvancedConfig({
                         : undefined,
                     })
                   }
-                  placeholder="2"
+                  placeholder="1"
                   disabled={!testConfig.enabled}
                 />
               </div>