v0.2.1

A small follow-up to 0.2.0 that finishes the deferred Jyutping API
parity work, hardens CI, and exposes a sort entry point that lets
library users verify the crate's stable-sort guarantee directly.

Added

• JyutpingOverride struct (gated by collator-jyutping) with the same
  TOML schema as PinyinOverride but tone digits in 1..=6. Loadable
  via JyutpingOverride::load_from_file.
• JyutpingCollator::with_override(JyutpingOverride) -> Result<Self>
  for building an override-aware collator.
• JyutpingCollator::jyutping_of(&str) returns readings honoring any
  configured phrase or per-character overrides.
• AnyCollator::jyutping_with_override constructor.
• CLI accepts --config <path> together with --sort-by jyutping; the
  file is parsed as a JyutpingOverride (tone 1-6) when sort_by is
  Jyutping and as a PinyinOverride (tone 1-5) for the default mode.
• sort_indices_with<C>(&[String], &C) -> Vec<usize> exposes the sort
  permutation, which makes the index-tiebreak stability guarantee
  directly verifiable from outside the crate.
• Cargo.toml rust-version = "1.85" (MSRV declared, matching edition
  2024 requirement).
• .gitattributes enforcing LF line endings on text files (CSVs,
  Python scripts, generated PHF files), so Windows clones with default
  autocrlf don't corrupt build-time inputs.

Changed

• CI now runs on a ubuntu-latest/macos-latest/windows-latest
  matrix with fail-fast: false. Previously only Linux was tested,
  so Windows path / line-ending / IsTerminal behavior had no
  coverage.
• The error message for --config paired with an unsupported
  --sort-by is now "--config is not supported with --sort-by <scheme>" (was previously phrased as "only supported with
  --sort-by pinyin", which is now incorrect since jyutping also
  accepts overrides).
• Internal validate_syllable in src/override.rs is parameterized
  over the valid tone range so PinyinOverride and JyutpingOverride
  share the syllable-shape check.

Fixed

• Stability of equal-key inputs is now provable. Previous tests on
  duplicate strings could not actually verify that the unstable
  backend was promoted to stable behavior — the rubber-duck Phase 1
  review flagged this as a smoke-level test. With sort_indices_with
  exposed, proptest verifies the stronger property:
  for any input, equal-sort-key items preserve their input-order
  relative position.