fix(puter-js): size img2txt data URIs by decoded bytes (#3457)

Match speech2txt/speech2speech and reject on decoded payload size, not
data-URI string length. Base64 expands ~4/3, so string-length checks
falsely rejected valid images under the 10MB limit.

src/puter-js/src/modules/ai/ai.test.js

@@ -289,6 +289,26 @@ describe('ai.img2txt driver payloads', () => {
     it('img2txt rejects without a source', async () => {
         await expect(ai.img2txt({})).rejects.toMatchObject({ code: 'source_required' });
     });
+
+    it('img2txt sizes data URIs by decoded bytes, not string length', async () => {
+        FakeXHR.respondWith = () => ({ success: true, result: { text: 'ok' } });
+        const prefix = 'data:image/png;base64,';
+        // String length just over 10MB; base64 still decodes under the 10MB limit (~7.5MB).
+        const targetLen = 10 * 1024 * 1024 + 4;
+        let base64Len = targetLen - prefix.length;
+        base64Len += (4 - (base64Len % 4)) % 4;
+        const uri = prefix + 'A'.repeat(base64Len);
+        expect(uri.length).toBeGreaterThan(10 * 1024 * 1024);
+        await expect(ai.img2txt(uri)).resolves.toBe('ok');
+    });
+
+    it('img2txt rejects when decoded data-URI bytes exceed 10MB', async () => {
+        const prefix = 'data:image/png;base64,';
+        let base64Len = Math.ceil(((10 * 1024 * 1024) + 1) * 4 / 3);
+        base64Len += (4 - (base64Len % 4)) % 4;
+        const uri = prefix + 'A'.repeat(base64Len);
+        await expect(ai.img2txt(uri)).rejects.toMatchObject({ code: 'input_too_large' });
+    });
 });
 
 describe('ai.txt2speech driver payloads', () => {

src/puter-js/src/modules/ai/ocr.js

@@ -1,5 +1,5 @@
 import * as utils from '../../lib/utils.js';
-import { isBlobLike, isPlainObject } from './lib/args.js';
+import { dataUriByteLength, isBlobLike, isPlainObject } from './lib/args.js';
 
 /** @typedef {import('../../../types/modules/ai').Img2TxtOptions} Img2TxtOptions */
 
@@ -124,7 +124,7 @@ export async function img2txt (sourceOrOptions, optionsOrTestMode, testModeOrOpt
 
     if ( typeof options.source === 'string' &&
         options.source.startsWith('data:') &&
-        options.source.length > MAX_INPUT_SIZE ) {
+        dataUriByteLength(options.source) > MAX_INPUT_SIZE ) {
         throw { message: `Input size cannot be larger than ${ MAX_INPUT_SIZE}`, code: 'input_too_large' };
     }