Fix import: chimera_router_v2.1 -> chimera_router_v2_1

nexus_os_v2/__init__.py

@@ -29,7 +29,7 @@ Core modules:
   milvus_client             — Zilliz Cloud retrieval (Free-01 / Serverless-01)
   ernie_adapter             — Browser-sourced manual callback (yiyan.baidu.com)
   chimera_router            — Hybrid orchestrator (QWAVE + TWAVE)
-  chimera_router_v2.1       — Telemetry-integrated production router + cloud + fallback
+  chimera_router_v2_1       — Telemetry-integrated production router + cloud + fallback
   cloud_api_adapters        — DeepSeek, Qwen, Kimi, GLM, OpenAI, Claude
   gmr_scheduler             — VRAM-aware model rotation
   per_token_debug           — Telemetry schema for token-level tracking
@@ -108,7 +108,7 @@ from .pinecone_client import PineconeRetriever, MockPineconeRetriever, Retrieval
 from .milvus_client import MilvusRetriever, MockMilvusRetriever, MilvusResult
 from .ernie_adapter import ERNIEAdapter, MockERNIEAdapter, ERNIEEvidence
 from .chimera_router import ChimeraRouter, QWAVEBudget, RouterResult, RoutingDecision
-from .chimera_router_v2.1 import ChimeraRouterV2, ModelFallbackController
+from .chimera_router_v2_1 import ChimeraRouterV2, ModelFallbackController
 from .cloud_api_adapters import (
     CloudAPIManager, BaseCloudAdapter, CloudResponse,
     DeepSeekAdapter, QwenAdapter, KimiAdapter, GLMAdapter,