[alejandrogzi]

[0.0.9] - 2026-07-26

Added

• MetadataIter zero-copy metadata line iterator — a new iterator type in
  io::reader that scans the reader's shared mmap/owned buffer without
  allocating and yields comment lines (those beginning with #) in input
  order. Each yielded item is a &[u8] slice that borrows the reader's
  underlying buffer directly, stripping only trailing newline and optional \r
  bytes. This makes metadata extraction both allocation-free and safe to call on
  any chain input.

• Reader::metadata_lines() method — returns a MetadataIter over the
  original chain input. The iterator starts at byte 0 and scans forward,
  yielding every #-prefixed line encountered. It is exposed as part of the
  public API (MetadataIter is re-exported from the crate root).

• Comment-line resilience in the parser — parse_chains_sequential and
  locate_chain_ranges now skip #-prefixed lines alongside blank lines,
  so chain files that embed metadata comments (for example, output from other
  UCSC tools) are parsed correctly instead of causing errors.

Tests

• Two new tests validate the metadata iterator: one confirms zero-copy
  semantics by comparing raw pointer offsets against known input positions,
  and one verifies that a comment-free input yields an empty iterator.