Chords are built by stacking scale thirds rather than from a quality table,
so the chord follows the degree automatically -- in C major, Alt+3 on C gives
C major, on D gives D minor, on B gives B diminished. Toggling delegates to
toggleCell, so chord tones inherit hold-mode joining, splitting and trimming
unchanged.
Velocity keys act on the note under the cursor if there is one, and on the
default for new notes otherwise, announcing which. That avoids a mode switch
between setting a level to draw at and shaping dynamics after the fact.
Also fixes install.ps1 failing to resolve its own directory: $PSScriptRoot is
not reliably populated during parameter binding, so it is resolved in the body.
Tests cover chord quality per scale degree and range clamping.
