feat(enginex): CCCL-style algorithm factor replacement engine — 18 operator dispatch system

EngineX replaces the missing corex_gdn/corex_moe/corex_fa2 operator chain
that Sub168 has but our BI-V100 image lacks.

Architecture (mirrors CCCL dispatch/tuning/kernel three-layer system):
  Registry (policy_selector) → three-tier dispatch:
    Tier 1: Native .so via dlopen (libcorex_gdn.so, libixattn.so)
    Tier 2: ixformer Python ops (vendor-provided)
    Tier 3: PyTorch fallback (always available)

Critical fixes vs comp 168 docker log:
  - moe_topk_softmax: replacement for missing ixformer op
  - gdn_prefill: NaN-stable chunked impl (chunk_size=16)
  - gdn_decode: state clamp prevents NaN accumulation

18 operators, all tests pass.

enginex/__init__.py

@@ -0,0 +1,16 @@
+"""
+EngineX — Algorithm Factor Replacement Engine for BI-V100
+
+Architecture modeled after CCCL's dispatch/tuning/kernel three-layer system:
+  CCCL:     tuning_*.cuh  → dispatch_*.cuh  → kernel_*.cuh
+  EngineX:  tuning/*.py   → dispatch/*.py   → ops/*.py
+
+The engine dlopen()s native .so when available, falls back to PyTorch/ixformer.
+This is NOT an adapter — it's a full algorithm factor replacement layer.
+"""
+
+__version__ = "0.1.0"
+
+from enginex.dispatch.registry import OperatorRegistry, get_registry
+
+__all__ = ["OperatorRegistry", "get_registry"]