Fix screenshot: formato immagine corretto {type:image, data: base64, mimeType} (il framework usa block.data, non source.data)

extensions/firefox-bidi.ts

@@ -26,6 +26,7 @@
 import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";
 import { Type } from "typebox";
 import { spawn, execFile } from "node:child_process";
+import { readFileSync } from "node:fs";
 import { promisify } from "node:util";
 
 const execFileAsync = promisify(execFile);
@@ -367,10 +368,11 @@ export default function (pi: ExtensionAPI) {
           ),
         "screenshot",
       );
+      const pngB64 = readFileSync(r.path).toString("base64");
       return {
         content: [
           { type: "text", text: `Screenshot salvato in ${r.path} (${r.bytes} bytes)` },
-          { type: "image", image: r.path, mediaType: "image/png" },
+          { type: "image", data: pngB64, mimeType: "image/png" },
         ],
         details: r,
       };