v0.4.0

Added

• select accepts a per-line changed-line selector [path:]INDEX@L<set> that
  keeps an arbitrary subset of a sub-hunk's changed (+/-) lines, where
  <set> is an index list over the changed lines (L1,3, L1-2,4). Unlike
  INDEX@RANGE (added-side only, cut between two + lines, deletions atomic),
  it has no boundary restriction: a deletion surrounded by additions
  (+x -y +z) can be isolated, and the deletions and additions of a
  replacement can be separated across commits via the diff → stage → re-diff
  loop. Unselected deletions are kept as context (anchoring the hunk, so the
  old-side footprint is invariant and no --unidiff-zero is needed);
  unselected additions are dropped. A sub-hunk addressed by @L must be
  addressed once per invocation (exit 2 otherwise).
• list --json reports a changed_lines array per sub-hunk —
  [{i, kind, text}] with 1-based indices shared across deletions and
  additions — the machine-readable source for building @L selectors without
  parsing the diff body.

Tests

• Added unit and end-to-end coverage for the line-set selector: separating
  deletions from additions, isolating a deletion among additions, full-selection
  round-trip, the no-newline-at-EOF re-add edge, the once-per-invocation rule,
  and the changed_lines JSON numbering.