v1.7.0

Additive (MINOR) release: per-chord harmony annotations. Backward-compatible — a 1.0.0 pack is also
a valid 1.7.0 pack, and older readers ignore the new optional fields.

Added

• Per-chord harmony annotations (spec §6.3.1,
  §6.6): two OPTIONAL fields that annotate a chord's
  harmony for teaching/display, never grading (the honesty rule — a grader MUST NOT score
  them) — fn on the chord instance ({rn, q, deg}: Roman-numeral label, quality token, and
  the chord root's chromatic offset 0–11 above the active keys.json
  tonic, mirroring sd; the chord's as-played function, derivable so a Reader MAY compute it),
  and voicing on the chord template (a key-independent voicing-type string, e.g. open /
  shell / drop2). Function rides the instance and voicing the template because the same shape
  recurs across keys. fn's prose notes its boundary with a future song-level harmony track (the
  intended progression). Schema: fn on $defs/chord and voicing on $defs/template in
  schemas/arrangement.schema.json; exercised by the extended
  example (an Em chord as vi in G major). caged and guideTones from the FEP are deferred.