fix(read_file): return image bytes in MCP content so the model can see images (#488)

read_file on an image previously put the image bytes only in
structuredContent (for the preview widget) and sent the host model a
text-only summary ("Image file: ... (image/png)"). The model received
no image block, so reading an image was effectively a no-op for the
model — it could never actually see the image.

Add the image content block back into the `content` array while keeping
structuredContent unchanged, so:
- the host model receives the image and can analyze it
- the preview widget still renders from structuredContent as before

The previous "text-only for broad host compatibility" approach blinded
every host that can handle images, which is the common case.

Author: wonderwhy-er

src/handlers/filesystem-handlers.ts

@@ -147,8 +147,9 @@ export async function handleReadFile(args: unknown): Promise<ServerResult> {
 
         // Handle image files
         if (fileResult.metadata?.isImage) {
-            // For image files, keep content payload text-only for broad host compatibility.
-            // The preview widget reads image bytes from structuredContent.
+            // Return the image bytes in the MCP content array so the host model can
+            // actually see the image. structuredContent additionally carries the bytes
+            // for the preview widget to render.
             const imageData = typeof fileResult.content === 'string'
                 ? fileResult.content
                 : fileResult.content.toString('base64');
@@ -158,6 +159,11 @@ export async function handleReadFile(args: unknown): Promise<ServerResult> {
                     {
                         type: "text",
                         text: imageSummary
+                    },
+                    {
+                        type: "image",
+                        data: imageData,
+                        mimeType: fileResult.mimeType
                     }
                 ],
                 structuredContent: {