Add official RouteFM and SAVERouter adapters

[AIGNLAI]

Summary

• add a RouteFM adapter backed by the official frozen BGE checkpoint and behavioral-context episode format
• add a SAVERouter adapter backed by the official fixed-K sparse-supervision pipeline and paper benchmark profiles
• register both methods, add configs, pin official dependencies, and document the release in README News
• add the official BGE CLS plus L2 embedding implementation and native cost integration

Compatibility notes

• RouteFM defaults to the released BGE text checkpoint; the Qwen variant is intentionally rejected because it requires joint Qwen3-VL embeddings from a compatible service
• RouteFM converts its relative log-cost prediction back to the ORBIT training-cost scale
• SAVERouter fitting receives only acquired sparse observations, not the unrevealed dense matrix

Validation

• python compileall passed
• all 45 JSON configs parsed
• 39 unit and smoke tests passed
• official RouteFM BGE checkpoint downloaded from its immutable Hugging Face revision, checksum-verified, loaded on CPU, and produced finite score and cost tensors with shape (1, 2, 6)
• git diff --check passed