fix: writeFile for buffers >= 2GiB

[dyk1454683243-sudo]

Problem

gracefulFS.writeFile fails for buffers of 2GiB or larger:

RangeError [ERR_OUT_OF_RANGE]: The value of "length" is out of range. It must be >= 0 && <= 2147483647. Received 2147483648
    at Object.write (node:fs:848:5)
    at writeAll (node:fs:2224:6)

Node's callback writeFile (writeAll) calls the exported fs.write with the full buffer length. fs.write validates length as a signed 32-bit integer (uv_fs_write). fs.promises.writeFile already chunks, which is why native writeFile works on recent Node.

graceful-fs wraps writeFile for EMFILE retry, but writeAll still calls the real fs.write, so the patched path hits this cap.

Fix

Wrap the exported fs.write / fs.writeSync (the functions writeAll actually calls) and split binary writes larger than INT32_MAX (2147483647). String writes and smaller buffers are unchanged.

Tests

test/write-large-buffer.js spies on fs.write to prove chunking without requiring CI to write 2GiB. A writeFile case allocates a 2GiB buffer when possible and skips if allocation fails.

Fixes #256