v0.3.0 — serve sequence bases by id

[0.3.0] - 2026-07-24

Breaking release: the index now retains the indexed text and can serve the bases of any
sequence, so callers no longer need to keep their own copy of every reference.

Added

• FmIndex::sequence(SeqId) / BidirFmIndex::sequence(SeqId) — the bases of one indexed
  sequence as a borrowed slice, in O(1), with the trailing sentinel excluded. Returns
  alphabet codes (A = 1, C = 2, …), not ASCII; use decode_char to render them.
• FmIndex::sequence_by_header(&str) / BidirFmIndex::sequence_by_header(&str) — the same
  by header, equivalent to seq_id(h).and_then(|id| self.sequence(id)).
• encode_byte, encode_char and decode_char re-exported at the crate root, so callers
  can move queries into (and results out of) the alphabet's code space without reaching
  into the alphabet module.

Changed

• Breaking. The serialized layout gains a text field, so indexes written by 0.2.0 and
  earlier are rejected by from_bytes and must be rebuilt.
• The concatenated text is no longer dropped after BWT construction. This costs ~n bytes of
  resident and serialized size and forgoes a build-time peak-memory reduction, in exchange
  for random-access substrings. An FM-index can otherwise only recover text by LF-walking
  backwards one symbol at a time — far too slow for a caller rescoring a read against a
  candidate diagonal, which is the case this exists to serve.
• Only the forward half of a BidirFmIndex retains text. The reverse half's copy is a
  redundant reversal that is never served, so it is released at build time, keeping the
  overhead at ~n rather than ~2n.

Upgrading

Indexes written by 0.2.0 and earlier are rejected by from_bytes and must be rebuilt.

Full changelog: v0.2.0...v0.3.0