fix: use undici ProxyAgent for Anthropic API (native fetch ignores agent)

app/api/voice/chat/route.ts

@@ -2,7 +2,7 @@ export const dynamic = 'force-dynamic'
 export const runtime = 'nodejs'
 
 import { NextResponse } from 'next/server'
-import { HttpsProxyAgent } from 'https-proxy-agent'
+import { fetch as undiciFetch, ProxyAgent } from 'undici'
 
 import { voiceBus } from '@/lib/voice-bus'
 import { systemPrompt } from '@/lib/voice-prompts'
@@ -110,10 +110,11 @@ async function claudeRequest(system: string, messages: any[], tools?: any[]): Pr
   }
 
   if (ANTHROPIC_PROXY) {
-    fetchOptions.agent = new HttpsProxyAgent(ANTHROPIC_PROXY)
+    fetchOptions.dispatcher = new ProxyAgent(ANTHROPIC_PROXY)
   }
 
-  const res = await fetch('https://api.anthropic.com/v1/messages', fetchOptions)
+  const fetchFn = ANTHROPIC_PROXY ? undiciFetch : fetch
+  const res = await fetchFn('https://api.anthropic.com/v1/messages', fetchOptions)
 
   if (!res.ok) {
     const err = await res.text()