Add DeepSeek Engram layer

Author: shuningjin

pytest.ini

@@ -21,6 +21,7 @@ addopts =
     --ignore=tests/unit/qwen3_omni_layers_test.py
     --ignore=tests/unit/qwen3_next_vs_reference_test.py
     --ignore=tests/unit/deepseek32_vs_reference_test.py
+    --ignore=tests/unit/engram_vs_reference_test.py
 markers =
     tpu_only: marks tests to be run on TPUs only
     gpu_only: marks tests to be run on GPUs only