[bugfix] fix prompt_adapter interleaved_content_convert_to_raw (#696)

# What does this PR do?

- fix interleaved_content_convert_to_raw in prompt_adapter to correctly
convert ImageContentItem to RawMediaItem with raw data bytes

## Test Plan

```
torchrun $CONDA_PREFIX/bin/pytest -v -s -k "meta_reference" --inference-model="meta-llama/Llama-3.2-11B-Vision-Instruct" ./llama_stack/providers/tests/inference/test_vision_inference.py
```

**Before**
<img width="844" alt="image"
src="https://github.com/user-attachments/assets/f2784b42-2e36-4477-9041-903d5d628a68"
/>


**After**
<img width="836" alt="image"
src="https://github.com/user-attachments/assets/362b6e47-29f7-4119-bcf3-f75db842735f"
/>


## Sources

Please link relevant resources if necessary.


## Before submitting

- [ ] This PR fixes a typo or improves the docs (you can dismiss the
other checks if that's the case).
- [ ] Ran pre-commit to handle lint / formatting issues.
- [ ] Read the [contributor
guideline](https://github.com/meta-llama/llama-stack/blob/main/CONTRIBUTING.md),
      Pull Request section?
- [ ] Updated relevant documentation.
- [ ] Wrote necessary unit or integration tests.

llama_stack/providers/utils/inference/prompt_adapter.py

@@ -40,7 +40,6 @@ from llama_stack.apis.common.content_types import (
     InterleavedContent,
     InterleavedContentItem,
     TextContentItem,
-    URL,
 )
 
 from llama_stack.apis.inference import (
@@ -117,27 +116,31 @@ async def interleaved_content_convert_to_raw(
         elif isinstance(c, TextContentItem):
             return RawTextItem(text=c.text)
         elif isinstance(c, ImageContentItem):
-            # load image and return PIL version
-            img = c.data
-            if isinstance(img, URL):
-                if img.uri.startswith("data"):
-                    match = re.match(r"data:image/(\w+);base64,(.+)", img.uri)
+            if c.url:
+                # Load image bytes from URL
+                if c.url.uri.startswith("data"):
+                    match = re.match(r"data:image/(\w+);base64,(.+)", c.url.uri)
                     if not match:
-                        raise ValueError("Invalid data URL format")
+                        raise ValueError(
+                            f"Invalid data URL format, {c.url.uri[:40]}..."
+                        )
                     _, image_data = match.groups()
                     data = base64.b64decode(image_data)
-                elif img.uri.startswith("file://"):
-                    path = img.uri[len("file://") :]
+                elif c.url.uri.startswith("file://"):
+                    path = c.url.uri[len("file://") :]
                     with open(path, "rb") as f:
                         data = f.read()  # type: ignore
-                elif img.uri.startswith("http"):
+                elif c.url.uri.startswith("http"):
                     async with httpx.AsyncClient() as client:
-                        response = await client.get(img.uri)
+                        response = await client.get(c.url.uri)
                         data = response.content
                 else:
                     raise ValueError("Unsupported URL type")
-            else:
+            elif c.data:
                 data = c.data
+            else:
+                raise ValueError("No data or URL provided")
+
             return RawMediaItem(data=data)
         else:
             raise ValueError(f"Unsupported content type: {type(c)}")