Interface sounds (apps/starter/assets/sounds/*.wav and copies made from them)

Derived from Google's Material Design sound resources, (c) Google,
https://m2.material.io/design/sound/sound-resources.html
licensed under Creative Commons Attribution 4.0 International (CC BY 4.0),
https://creativecommons.org/licenses/by/4.0/

Changes: mixed to mono, trimmed, shortened, faded, normalized and converted to
16-bit 48 kHz WAV by tools/ui_sounds.mjs, and renamed:
  focus.wav    <- navigation_hover-tap
  confirm.wav  <- navigation_forward-selection-minimal
  back.wav     <- navigation_backward-selection-minimal
  error.wav    <- navigation_unavailable-selection
  page.wav     <- ui_tap-variant-01
  notify.wav   <- notification_simple-01
