Initial K3 snapshot: 0.5B KDA/MLA/MoE train path

Standalone tree split from LLMRL/projects/kda. Includes Triton dt_bias
backward fix, train_k3 --preset 0.5b, SFT, Docker runtime, and tests.

tests/integration/test_eval_mt.py

@@ -0,0 +1,44 @@
+"""translation_success and eval helpers (no GPU, no FLORES download)."""
+from kda.training.success import translation_success
+
+
+def test_empty_and_copy_fail():
+    src = "人工智能的发展改变了世界。"
+    assert translation_success(src, "", ref="The development of AI changed the world.", target_lang="en") is False
+    assert translation_success(src, src, ref="The development of AI changed the world.", target_lang="en") is False
+
+
+def test_wrong_language_fails():
+    src = "The cat sat on the mat."
+    hyp = "The cat sat on the mat and smiled."
+    ref = "猫坐在垫子上。"
+    assert translation_success(src, hyp, ref, target_lang="zh") is False
+
+
+def test_instruction_leak_fails():
+    src = "Hello"
+    hyp = "翻译如下：你好"
+    assert translation_success(src, hyp, ref="你好", target_lang="zh") is False
+
+
+def test_good_zh2en_passes():
+    src = "今天天气很好。"
+    hyp = "The weather is very nice today."
+    ref = "The weather is very nice today."
+    assert translation_success(src, hyp, ref, target_lang="en") is True
+
+
+def test_container_help_exits_2():
+    import importlib.util
+    from pathlib import Path
+
+    import pytest
+
+    path = Path(__file__).resolve().parents[2] / "scripts" / "container_help.py"
+    spec = importlib.util.spec_from_file_location("container_help", path)
+    mod = importlib.util.module_from_spec(spec)
+    assert spec.loader is not None
+    spec.loader.exec_module(mod)
+    with pytest.raises(SystemExit) as ei:
+        mod.main()
+    assert ei.value.code == 2