feat: support big file downloads (read from WA cache + streaming) (#201697)

* feat: support big file downloads (read from WA cache + streaming)

* fix: simplify downloadMediaStream to use a single handle

instead of two handles (resultHandle + blobHandle) with disposal gaps,
get the blob handle directly from evaluateHandle and read metadata
via blobHandle.evaluate. This eliminates the intermediate resultHandle
entirely.

blobhandle is disposed in all exit paths: null metadata, evaluate
error, and generator finally.

example.js

@@ -1,3 +1,4 @@
+const fs = require('fs');
 const { Client, Location, Poll, List, Buttons, LocalAuth } = require('./index');
 
 const client = new Client({
@@ -233,6 +234,18 @@ client.on('message', async (msg) => {
             Platform: ${info.platform}
         `,
         );
+    } else if (msg.body === '!streamdownload' && msg.hasMedia) {
+        const result = await msg.downloadMediaStream();
+        if (result) {
+            const filePath = `./${result.filename || 'download'}`;
+            const writeStream = fs.createWriteStream(filePath);
+            result.stream.pipe(writeStream);
+            writeStream.on('finish', () => {
+                msg.reply(
+                    `Media saved to ${filePath} (${result.mimetype}, ${result.filesize} bytes)`,
+                );
+            });
+        }
     } else if (msg.body === '!mediainfo' && msg.hasMedia) {
         const attachmentData = await msg.downloadMedia();
         msg.reply(`