Kate + SPV + Engine · fit guide
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SPLIT
  Kate          edit SPV sources + single sheet HTML
  engine binary paint single sheet SDF (X11 GL · no browser)
  webbrowser/   plug library (js_all, fox, stream, protos…) ESSIE seats

NO FIREFOX REQUIRED
  Primary:  ./RTXLayer/rtx engine
  Sheet:    engine/sheets/essie_menu.html
  Edit:     wb kate sheet | wb kate js_all | wb kate fox

100% PLUGS (menu-launched)
  html5_all  HTML 100%
  css_all    CSS 100%
  js_all     JS 100%   ← commands suite
  fox        typing speedtest + train (not JS)

EMPTY START
  Desktop pack opens with zero tabs · Start/menu only

ENGINE FIT
  engine.c already: HTML5+CSS subset · raised-SDF · SPV compute linear BGS→BGF
  Done Issue4: load sheets/essie_menu.html as default ui · hit-test menu buttons
  Next deepen: mount pack plugs from native engine seats
  Full pack JS still optional intermediate until native mounts expand

COMMANDS
  rtx engine
  wb kate
  wb sheet          # show sheet path / regenerate note
  wb pack