Implements binary file parsing with stack reconstruction. On Unix,
uses mmap with MADV_SEQUENTIAL for efficient sequential access. Falls
back to buffered I/O on Windows.

The reader reconstructs full stacks from delta-encoded records by
maintaining per-thread state. Each sample's stack is rebuilt by
applying the encoded operation (repeat/suffix/pop-push) to the
previous stack for that thread.

Replay feeds reconstructed samples to any collector, enabling
conversion between formats without re-profiling.