Recognize ANTHROPIC_AUTH_TOKEN in setup verification

The credential proxy already reads ANTHROPIC_AUTH_TOKEN (credential-proxy.ts
line 33) and uses it for OAuth-mode authentication, but setup/verify.ts did
not include it in its credential-detection regex.  Users with
ANTHROPIC_AUTH_TOKEN in .env saw 'CREDENTIALS: missing' even though their
credentials were valid at runtime.

Add ANTHROPIC_AUTH_TOKEN to the regex and add a matching test case.

Closes gh-853

setup/verify.ts

@@ -139,7 +139,7 @@ export async function run(_args: string[]): Promise<void> {
   const envFile = path.join(projectRoot, '.env');
   if (fs.existsSync(envFile)) {
     const envContent = fs.readFileSync(envFile, 'utf-8');
-    if (/^(CLAUDE_CODE_OAUTH_TOKEN|ANTHROPIC_API_KEY|ONECLI_URL)=/m.test(envContent)) {
+    if (/^(CLAUDE_CODE_OAUTH_TOKEN|ANTHROPIC_API_KEY|ANTHROPIC_AUTH_TOKEN|ONECLI_URL)=/m.test(envContent)) {
       credentials = 'configured';
     }
   }