feat: cf_core.reranker — shared reranker module Phase 1 (#54)
Trunk + text branch + BGE adapter:
- base.py: Reranker Protocol, RerankResult (frozen dataclass), TextReranker
base class with rerank() / rerank_batch() built on _score_pairs()
- adapters/mock.py: MockTextReranker — Jaccard scoring, no deps, deterministic
- adapters/bge.py: BGETextReranker — FlagEmbedding cross-encoder, thread-safe,
batched forward pass via rerank_batch(); graceful ImportError if dep missing
- __init__.py: rerank() singleton, make_reranker(), reset_reranker();
CF_RERANKER_MODEL / CF_RERANKER_BACKEND / CF_RERANKER_MOCK env vars
- pyproject.toml: reranker-bge and reranker-qwen3 optional dep groups
- 20 tests, all passing
Architecture ready for Phase 2 (Qwen3TextReranker) and Phase 3 (cf-orch remote
backend). ImageReranker/AudioReranker branches stubbed in base.py docstring.
pyr0ball
82f0b4c3d0