fix: gate preconnectAnthropicApi behind isEssentialTrafficOnly()

CC_Pure:  was the last un-gated outbound
connection — it unconditionally sent a TCP+TLS handshake to
api.anthropic.com on every startup. Now checked against the central
privacy gate (CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC=1) and
skipped when enabled.

Verified via strace: zero remote connections after fix.

src/utils/apiPreconnect.ts

@@ -25,6 +25,7 @@
 
 import { getOauthConfig } from '../constants/oauth.js'
 import { isEnvTruthy } from './envUtils.js'
+import { isEssentialTrafficOnly } from './privacyLevel.js'
 
 let fired = false
 
@@ -32,6 +33,9 @@ export function preconnectAnthropicApi(): void {
   if (fired) return
   fired = true
 
+  // CC_Pure: skip preconnect when non-essential traffic is disabled
+  if (isEssentialTrafficOnly()) return
+
   // Skip if using a cloud provider — different endpoint + auth
   if (
     isEnvTruthy(process.env.CLAUDE_CODE_USE_BEDROCK) ||