Read the kernel cache with FASTH3_KERNEL_CACHE_TOKEN when set

The org Space's HF_TOKEN cannot read the private multimodalart cache repo.

fasth3_engine.py

@@ -57,7 +57,8 @@ def fetch_kernel_cache() -> bool:
 
     t0 = time.time()
     try:
-        archive = hf_hub_download(KERNEL_CACHE_REPO, kernel_cache_name(), repo_type="dataset", token=_hf_token())
+        token = os.getenv("FASTH3_KERNEL_CACHE_TOKEN") or _hf_token()
+        archive = hf_hub_download(KERNEL_CACHE_REPO, kernel_cache_name(), repo_type="dataset", token=token)
         with tarfile.open(archive) as tar:
             tar.extractall(KERNEL_CACHE_DIR, filter="tar")
     except Exception as error: