fix: integer overflow in CombinedStream.Write for files >2GB

[Cryotechnic]

Problem

CombinedStream.Write crashes with ArgumentOutOfRangeException (parameter 'count') when writing to output files larger than ~2.1GB.

The root cause is an unchecked (int) cast:

int remainedMaxLength = (int)(_underlyingStreams[_index].Length - _underlyingStreams[_index].Position);

When Length - Position exceeds Int32.MaxValue (e.g. a 3GB file at position 0), the cast overflows to a large negative number. This negative value is then passed as count to FileStream.Write, which throws.

Affected Scenario

• Directory-level HDiff patches (HDIFF19 + HDIFF13) producing output files larger than 2GB. Specifically hit with Wuthering Waves pakchunk files ranging from 3-7GB.

Fix

Cap the remaining length to int.MaxValue before the cast using Math.Min. This is safe because count (the bytes to write) is always <= int.MaxValue, so the comparison remainedMaxLength < count still works correctly.\n\nBoth Write(ReadOnlySpan<byte>) and Write(byte[], int, int) overloads are fixed.