fix(failover): patch P1-P3 reliability gaps surfaced by team review

- Forwarder buffers non-streaming bodies and primes streaming first
  chunk before signaling success, so body timeouts and SSE first-chunk
  failures route through the circuit breaker instead of being recorded
  as success on response-header arrival
- Atomic enable-failover: switch to P1 before persisting the flag, and
  roll back auto-added queue entries when the switch is rejected
  (e.g. official providers)
- Hot-reload circuit breaker config on per-app proxy config change
  instead of waiting for a proxy restart
- FailoverToggle / FailoverQueueManager / AutoFailoverConfigPanel
  require proxy takeover for the active app; the backend command also
  rejects enabling when takeover is off
- ProviderHealthBadge consumes the backend is_healthy flag instead of
  hardcoding the 5-failure threshold

Cleanup:
- impl From<&AppProxyConfig> for CircuitBreakerConfig and use it from
  the command layer
- Collapse three identical TabsContent blocks into a single map

src/components/providers/ProviderCard.tsx

@@ -364,6 +364,7 @@ export function ProviderCard({
               {isProxyRunning && isInFailoverQueue && health && (
                 <ProviderHealthBadge
                   consecutiveFailures={health.consecutive_failures}
+                  isHealthy={health.is_healthy}
                 />
               )}
 

src/components/providers/ProviderHealthBadge.tsx

@@ -4,6 +4,7 @@ import { useTranslation } from "react-i18next";
 
 interface ProviderHealthBadgeProps {
   consecutiveFailures: number;
+  isHealthy?: boolean;
   className?: string;
 }
 
@@ -13,6 +14,7 @@ interface ProviderHealthBadgeProps {
  */
 export function ProviderHealthBadge({
   consecutiveFailures,
+  isHealthy,
   className,
 }: ProviderHealthBadgeProps) {
   const { t } = useTranslation();
@@ -29,7 +31,7 @@ export function ProviderHealthBadge({
         bgColor: "bg-green-500/10",
         textColor: "text-green-600 dark:text-green-400",
       };
-    } else if (consecutiveFailures < 5) {
+    } else if (isHealthy !== false) {
       return {
         labelKey: "health.degraded",
         labelFallback: "降级",

src/components/proxy/FailoverToggle.tsx

@@ -10,6 +10,7 @@ import {
   useAutoFailoverEnabled,
   useSetAutoFailoverEnabled,
 } from "@/lib/query/failover";
+import { useProxyStatus } from "@/hooks/useProxyStatus";
 import { cn } from "@/lib/utils";
 import { useTranslation } from "react-i18next";
 import type { AppId } from "@/lib/api";
@@ -24,8 +25,11 @@ export function FailoverToggle({ className, activeApp }: FailoverToggleProps) {
   const { data: isEnabled = false, isLoading } =
     useAutoFailoverEnabled(activeApp);
   const setEnabled = useSetAutoFailoverEnabled();
+  const { takeoverStatus } = useProxyStatus();
+  const takeoverEnabled = takeoverStatus?.[activeApp] ?? false;
 
   const handleToggle = (checked: boolean) => {
+    if (checked && !takeoverEnabled) return;
     setEnabled.mutate({ appType: activeApp, enabled: checked });
   };
 
@@ -36,15 +40,20 @@ export function FailoverToggle({ className, activeApp }: FailoverToggleProps) {
         ? "Codex"
         : "Gemini";
 
-  const tooltipText = isEnabled
-    ? t("failover.tooltip.enabled", {
+  const tooltipText = !takeoverEnabled
+    ? t("failover.tooltip.takeoverRequired", {
         app: appLabel,
-        defaultValue: `${appLabel} 故障转移已启用\n按队列优先级（P1→P2→...）选择供应商`,
+        defaultValue: `请先接管 ${appLabel}，再启用故障转移`,
       })
-    : t("failover.tooltip.disabled", {
-        app: appLabel,
-        defaultValue: `启用 ${appLabel} 故障转移\n将立即切换到队列 P1，并在失败时自动切换到下一个`,
-      });
+    : isEnabled
+      ? t("failover.tooltip.enabled", {
+          app: appLabel,
+          defaultValue: `${appLabel} 故障转移已启用\n按队列优先级（P1→P2→...）选择供应商`,
+        })
+      : t("failover.tooltip.disabled", {
+          app: appLabel,
+          defaultValue: `启用 ${appLabel} 故障转移\n将立即切换到队列 P1，并在失败时自动切换到下一个`,
+        });
 
   return (
     <div
@@ -69,7 +78,7 @@ export function FailoverToggle({ className, activeApp }: FailoverToggleProps) {
       <Switch
         checked={isEnabled}
         onCheckedChange={handleToggle}
-        disabled={setEnabled.isPending || isLoading}
+        disabled={setEnabled.isPending || isLoading || !takeoverEnabled}
       />
     </div>
   );

src/components/proxy/ProxyPanel.tsx

@@ -725,6 +725,7 @@ function ProviderQueueItem({
       {/* 健康徽章 */}
       <ProviderHealthBadge
         consecutiveFailures={health?.consecutive_failures ?? 0}
+        isHealthy={health?.is_healthy}
       />
     </div>
   );

src/components/settings/ProxyTabContent.tsx

@@ -35,6 +35,7 @@ export function ProxyTabContent({
 
   const {
     isRunning,
+    takeoverStatus,
     startProxyServer,
     stopWithRestore,
     isPending: isProxyPending,
@@ -176,72 +177,38 @@ export function ProxyTabContent({
                   <TabsTrigger value="codex">Codex</TabsTrigger>
                   <TabsTrigger value="gemini">Gemini</TabsTrigger>
                 </TabsList>
-                <TabsContent value="claude" className="mt-4 space-y-6">
-                  <div className="space-y-4">
-                    <div>
-                      <h4 className="text-sm font-semibold">
-                        {t("proxy.failoverQueue.title")}
-                      </h4>
-                      <p className="text-xs text-muted-foreground">
-                        {t("proxy.failoverQueue.description")}
-                      </p>
-                    </div>
-                    <FailoverQueueManager
-                      appType="claude"
-                      disabled={!isRunning}
-                    />
-                  </div>
-                  <div className="border-t border-border/50 pt-6">
-                    <AutoFailoverConfigPanel
-                      appType="claude"
-                      disabled={!isRunning}
-                    />
-                  </div>
-                </TabsContent>
-                <TabsContent value="codex" className="mt-4 space-y-6">
-                  <div className="space-y-4">
-                    <div>
-                      <h4 className="text-sm font-semibold">
-                        {t("proxy.failoverQueue.title")}
-                      </h4>
-                      <p className="text-xs text-muted-foreground">
-                        {t("proxy.failoverQueue.description")}
-                      </p>
-                    </div>
-                    <FailoverQueueManager
-                      appType="codex"
-                      disabled={!isRunning}
-                    />
-                  </div>
-                  <div className="border-t border-border/50 pt-6">
-                    <AutoFailoverConfigPanel
-                      appType="codex"
-                      disabled={!isRunning}
-                    />
-                  </div>
-                </TabsContent>
-                <TabsContent value="gemini" className="mt-4 space-y-6">
-                  <div className="space-y-4">
-                    <div>
-                      <h4 className="text-sm font-semibold">
-                        {t("proxy.failoverQueue.title")}
-                      </h4>
-                      <p className="text-xs text-muted-foreground">
-                        {t("proxy.failoverQueue.description")}
-                      </p>
-                    </div>
-                    <FailoverQueueManager
-                      appType="gemini"
-                      disabled={!isRunning}
-                    />
-                  </div>
-                  <div className="border-t border-border/50 pt-6">
-                    <AutoFailoverConfigPanel
-                      appType="gemini"
-                      disabled={!isRunning}
-                    />
-                  </div>
-                </TabsContent>
+                {(["claude", "codex", "gemini"] as const).map((appType) => {
+                  const failoverDisabled =
+                    !isRunning || !(takeoverStatus?.[appType] ?? false);
+                  return (
+                    <TabsContent
+                      key={appType}
+                      value={appType}
+                      className="mt-4 space-y-6"
+                    >
+                      <div className="space-y-4">
+                        <div>
+                          <h4 className="text-sm font-semibold">
+                            {t("proxy.failoverQueue.title")}
+                          </h4>
+                          <p className="text-xs text-muted-foreground">
+                            {t("proxy.failoverQueue.description")}
+                          </p>
+                        </div>
+                        <FailoverQueueManager
+                          appType={appType}
+                          disabled={failoverDisabled}
+                        />
+                      </div>
+                      <div className="border-t border-border/50 pt-6">
+                        <AutoFailoverConfigPanel
+                          appType={appType}
+                          disabled={failoverDisabled}
+                        />
+                      </div>
+                    </TabsContent>
+                  );
+                })}
               </Tabs>
             </div>
           </AccordionContent>