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.

modules/home/hyprland.nix

@@ -1026,15 +1026,14 @@ in
         "float 1, match:class (?i)^(\\.?blueman-(manager|adapters)(-wrapped)?|\\.?system-config-printer(-wrapped)?)$"
         "center 1, match:class (?i)^(\\.?blueman-(manager|adapters)(-wrapped)?|\\.?system-config-printer(-wrapped)?)$"
 
-        # Calendar popup (item 42): the Waybar clock's on-click runs
-        # nomarchy-calendar → calcurse in a ghostty window tagged with a
-        # distinct --class, so it floats centered instead of tiling.
+        # Calendar popup (item 42): nomarchy-calendar → calcurse in a
+        # kitty window tagged with a distinct --class, so it floats centered.
         "float 1, match:class ^(com\\.nomarchy\\.calendar)$"
         "size 60% 65%, match:class ^(com\\.nomarchy\\.calendar)$"
         "center 1, match:class ^(com\\.nomarchy\\.calendar)$"
 
         # Doctor sheet (System › Doctor / Waybar custom/doctor click):
-        # nomarchy-menu doctor → ghostty --class=com.nomarchy.doctor.
+        # nomarchy-menu doctor → kitty --class=com.nomarchy.doctor.
         "float 1, match:class ^(com\\.nomarchy\\.doctor)$"
         "size 55% 70%, match:class ^(com\\.nomarchy\\.doctor)$"
         "center 1, match:class ^(com\\.nomarchy\\.doctor)$"