Release 0.9.1

- Add a "Searching..." overlay (and a live terminal progress counter) shown while
  S / Shift+S scan for the next / previous selector-matched event, so a slow scan no
  longer looks like a frozen window
- Validate the event selector before launch (run it on the first event and confirm a
  match) so a broken selector fails fast instead of hanging or crashing
- Add startup status messages announcing each slow step (opening files, drawing the
  geometry, calibrating the first event, scene / shader compilation), with a
  rainbow-tinted ">>>" prefix
- Restyle the "Searching..." overlay with a muted grey palette
- Improve the MC / hits printout