feat: add image metadata loader with native LoRA Manager integration

Add Load Image Metadata (LoraManager) to extract reusable prompts,
model references, LoRA stacks, and sampling settings from images.

Prefer saved A1111-style parameters by default, with optional workflow
and subgraph sampler selection. Resolve local model and LoRA names,
report missing resources, and recover extraction failures with explicit
defaults and readable diagnostics.

Include parser, resource-resolution, and node regression tests, plus
usage documentation.

py/utils/exif_utils.py

@@ -177,6 +177,11 @@ class ExifUtils:
                 return brotli_meta
 
         with Image.open(image_path) as img:
+            # PNG text chunks may legally follow IDAT. Pillow reads those only
+            # when loading the image, so inspecting info immediately after open
+            # can incorrectly report a metadata-free image.
+            if img.format == "PNG":
+                img.load()
             info = getattr(img, "info", {}) or {}
 
             if "parameters" in info:
@@ -193,6 +198,18 @@ class ExifUtils:
                         exif[piexif.ExifIFD.UserComment]
                     )
 
+            # ComfyUI's WebP exporter stores JSON in EXIF Make/Model with
+            # prompt:/workflow: prefixes instead of UserComment.
+            exif = img.getexif()
+            for tag in (piexif.ImageIFD.Make, piexif.ImageIFD.Model):
+                text = ExifUtils._decode_exif_text(exif.get(tag))
+                if not text:
+                    continue
+                for key in ("prompt", "workflow"):
+                    prefix = key + ":"
+                    if text.startswith(prefix) and not metadata[key]:
+                        metadata[key] = text[len(prefix):].rstrip("\x00")
+
             try:
                 exif_dict = piexif.load(image_path)
             except Exception as e: