feat: --stream-layers for streaming weights from CPU during generation (#1576)

include/stable-diffusion.h

@@ -222,6 +222,7 @@ typedef struct {
     bool qwen_image_zero_cond_t;
     enum sd_vae_format_t vae_format;
     float max_vram;  // GiB budget for graph-cut segmented param offload (0 = disabled, -1 = auto free VRAM minus 1 GiB)
+    bool stream_layers;  // Enable residency+prefetch streaming on top of --max-vram (no effect without --max-vram)
     const char* backend;
     const char* params_backend;
 } sd_ctx_params_t;