from pathlib import Path

base = Path(__file__).resolve().parent
parts = [base / ".part1.md", base / ".part2.md", base / ".part3.md"]
out = base / "Королевство 5 — глубокий анализ и разбор.md"
out.write_bytes(b"".join(part.read_bytes() for part in parts))
print(out)