refactor: remove token-refresh, use env-based auth only

Delete token-refresh.ts and credentials.json sync. Auth is now
via CLAUDE_CODE_OAUTH_TOKEN in .env (1-year setup-token).
No more auto-refresh loop or credentials.json dependency.

src/agent-runner.ts

@@ -63,13 +63,6 @@ function prepareGroupEnvironment(
   );
   fs.mkdirSync(groupSessionsDir, { recursive: true });
 
-  // Sync credentials from user's home ~/.claude/ so per-group sessions stay fresh
-  const homeClaudeDir = path.join(os.homedir(), '.claude');
-  const credsSrc = path.join(homeClaudeDir, '.credentials.json');
-  if (fs.existsSync(credsSrc)) {
-    fs.copyFileSync(credsSrc, path.join(groupSessionsDir, '.credentials.json'));
-  }
-
   const settingsFile = path.join(groupSessionsDir, 'settings.json');
   if (!fs.existsSync(settingsFile)) {
     fs.writeFileSync(