Create instruction.txt in evaluation sandboxes

[sail-amir]

Summary

This PR writes each problem's instruction to instruction.txt when creating an evaluation sandbox.

Some JavaScript/React tests read ../instruction.txt directly. The current sandbox setup writes files such as original_code.jsx, implementation1.jsx, and tests/test_code.test.js, but does not write instruction.txt, so these tests can fail before any assertions run.

Affected example

Problem 83 fails during Jest setup because its test reads:

const instruction = fs.readFileSync(path.join(__dirname, '../instruction.txt'), 'utf8').trim();

Before this fix, the failure is:

ENOENT: no such file or directory, open '/root/editbench_sandboxes/question_83/instruction.txt'
Tests: 0 total
No test results found at /root/editbench_sandboxes/question_83/test_results.json

This affects the full translated problem family because all variants share the same pair_id and test structure:

pair_id: c7f2ad26-828e-4bc0-a2d1-ec8171ff195a

83   english   javascript/react   adjust width according to content
212  chinese   javascript/react   根据内容调整宽度
309  russian   javascript/react   регулируйте ширину в соответствии с содержимым
414  polish    javascript/react   dostosuj szerokość do zawartości
519  spanish   javascript/react   ajustar el ancho según el contenido

Fix

Create instruction.txt in each question sandbox from question["instruction"].

The change is intentionally small:

with open(curr_dir / "instruction.txt", "w") as f:
    f.write(question["instruction"])