Add Royal Road vaporwave as a committed, reproducible capability

We once rendered ten vaporwave tracks into an unversioned home dir; the renders survived but the .csd that made them was lost, then the renders themselves were deleted.

• This fixes it the way the rest of the repo works: source is the artifact, renders are derived.

• royal-road.csd — the capability (Fmaj7-G7-Em7-Am7, ~70 BPM, detuned saw pads, tape-wow wobble, hall reverb). Renders cleanly under csound 6.18, no clipping.

• render.sh — one command back from text to sound.

• .gitignore — *.wav/*.mp3 derived, never committed.

▶ Play it: Food Court Eternity — parked on the genre this change names https://stellate.app/?genre=vaporwave&seed=9244&path=1679.4393,1698.4426,1660.4426&xdur=13.122

4b0af4d https://github.com/aboard-io/stellate/commit/4b0af4dc75ab553eed6ec853ce7d3051133ce0cc