Add canawave genre: proud Canadiana pop with engine additions

A bright major-key Canadian pop anchor — arpeggiated/distorted guitar, toms + hi-hats, loon calls, the national news, and a Stephen Leacock narration bed — plus the engine vocabulary it needed.

• real tom instrument (instr 13) + descending tom-roll "tom fill" (was a snare roll)

• real sampled hi-hats via GM soundfont sfplay (state.realHats); rhodes + organ pad voices; `kpluck` Karplus-Strong guitar (octave-down, body resonance, pick attack, distortion, chorus, octave doubling) and an…

• countermelody layer (sec.counter) so a brass section / arpeggiated guitar can play over the lead

• per-sample reverb/delay/fade sends on instr 5 (distant horn "across the lake", glitched faded loon, glitched-but-coherent voiceover that no longer 2x-loops)

▶ Play it: Loon Referendum — parked on the genre this change names https://stellate.app/?genre=canawave&seed=8578&path=1505.3698,1524.3731,1486.3731&xdur=13.122

5e10e93 https://github.com/aboard-io/stellate/commit/5e10e9320bcf10a37004fe6a117b34780f5b1ae3