feat: add PuLID-Flux identity-injection support (#1595)

src/model/diffusion/model.hpp

@@ -22,6 +22,11 @@ struct SkipLayerDiffusionExtra {
 struct FluxDiffusionExtra {
     const sd::Tensor<float>* guidance   = nullptr;
     const std::vector<int>* skip_layers = nullptr;
+    // PuLID-Flux: precomputed (N=1, num_tokens=32, kv_dim=2048) identity embedding
+    // produced by runtime-scripts/pulid_extract_id.py. nullptr when PuLID is
+    // disabled. id_weight is per-job (typical 0.7-1.2; default 1.0).
+    const sd::Tensor<float>* pulid_id   = nullptr;
+    float pulid_id_weight               = 1.0f;
 };
 
 struct AnimaDiffusionExtra {