MemorySegment and Arena

FFM models native, off-heap memory with two central types: MemorySegment represents a contiguous region of memory, and Arena controls its lifetime.

Together they replace the unsafe manual buffer management of the past.

A MemorySegment is a typed window over a block of memory. It knows its size and its lifetime, and every access is bounds-checked.

Segments can be off-heap (native) or wrap an on-heap array.