feat(terminal): Kitty only — drop Ghostty (#95)

Ghostty's OpenGL 4.3 floor broke the Acer (HD 4000 / 4.2). Dual-terminal
support (default Ghostty + install-time Kitty fallback) was more complexity
than it was worth.

- Remove ghostty.nix / nomarchy.ghostty.enable
- Kitty always installed and themed from theme-state
- Default nomarchy.terminal = kitty; SUPER+Return, doctor, calendar,
  what-changed use kitty --class=com.nomarchy.*
- Drop install-time glxinfo probe and mesa-demos on the installer
- Docs/REQUIREMENTS no longer list OpenGL 4.3 as a terminal floor

Verified: V0 flake check; option-docs; installer-safety; template HM has
kitty, no ghostty; menu/calendar emit classed kitty launches.

hosts/live.nix

@@ -89,8 +89,9 @@ in
   # ISO is the desktop, so re-enable what it strips. Above all
   # fontconfig (upstream forces it off at mkOverride 500): without it
   # no configured family resolves — Waybar icons render as tofu and
-  # Ghostty silently falls back to the wrong font (seen on the
-  # Latitude 5410). Normal priority (100) beats the override.
+  # Kitty silently falls back to the wrong font (seen on the
+  # Latitude 5410 with Ghostty; same fontconfig footgun). Normal priority
+  # (100) beats the override.
   fonts.fontconfig.enable = true;
 
   # No boot splash on the install medium: the installer ISO boots its