feat: wire candle 0.9 + hf-hub as calibration deps (feature-gated)

Three tools, three roles:
  candle: Training (SiLU) + Forward Pass Ground Truth (Jina/BGE-M3/Qwen)
  ort:    Reranker Ground Truth (only path) + Bulk Calibration speed
  rten:   Medical Imaging Sensor (U-Net/ViT, pure Rust, separate)

New feature flag: --features calibration
  candle-core 0.9, candle-nn 0.9, candle-transformers 0.9, hf-hub 0.4
  All optional — default build unchanged (188 tests pass)

Follows EmbedAnything's proven versions (candle 0.9.2).
Jina BERT, ModernBERT, Qwen3 forward pass patterns available
from StarlightSearch/EmbedAnything/rust/src/models/ as reference.

ort for Reranker is next (separate dep, only needed for cross-encoder).

https://claude.ai/code/session_019RzHP8tpJu55ESTxhfUy1A

Author: claude