feat(claude-executor): add ZSTD decoding support for Claude executor responses

- Integrated ZSTD decompression via `github.com/klauspost/compress` for responses with "zstd" content-encoding.
- Added helper `hasZSTDEcoding` to detect ZSTD-encoded responses.
- Updated response handling logic to initialize and use a ZSTD decoder when necessary.

refactor(api-handlers): split streaming and non-streaming response handling

- Introduced `handleNonStreamingResponse` for processing non-streaming requests in `ClaudeCodeAPIHandler`.
- Improved code clarity by separating streaming and non-streaming logic.

fix(service): remove redundant token refresh interval assignment logic in `cliproxy` service.

sdk/cliproxy/service.go

@@ -322,9 +322,6 @@ func (s *Service) Run(ctx context.Context) error {
 	// Prefer core auth manager auto refresh if available.
 	if s.coreManager != nil {
 		interval := 15 * time.Minute
-		if sec := s.cfg.GeminiWeb.TokenRefreshSeconds; sec > 0 {
-			interval = time.Duration(sec) * time.Second
-		}
 		s.coreManager.StartAutoRefresh(context.Background(), interval)
 		log.Infof("core auth auto-refresh started (interval=%s)", interval)
 	}