feat(terminal): themed Kitty when OpenGL < 4.3 (#95)

Ghostty needs OpenGL 4.3; older GPUs (Intel HD 4000) top out at 4.2.
Installer probes glxinfo and writes settings.terminal=kitty into
theme-state when below the floor. modules/home/kitty.nix enables Kitty
with the same palette, mono font, and opacity as Ghostty so the fallback
still looks like Nomarchy.

Default machines stay Ghostty-only (no kitty in the HM closure). Doctor
and calendar still invoke Ghostty by class — V3 on Acer for SUPER+Return.

Verified: V0 flake check; installer-safety; HM with terminal=kitty builds
themed kitty.conf + TERMINAL=kitty; default template has no kitty bin.

modules/home/options.nix

@@ -101,9 +101,17 @@ in
     terminal = lib.mkOption {
       type = lib.types.str;
       default = config.nomarchy.settings.terminal or "ghostty";
-      description = "Terminal emulator command, used by keybinds and $TERMINAL.";
+      example = "kitty";
+      description = ''
+        Terminal emulator command, used by keybinds and `$TERMINAL`.
+        Default is Ghostty. On GPUs below OpenGL 4.3 the installer writes
+        `settings.terminal = "kitty"` so SUPER+Return still works (Ghostty
+        needs 4.3; see docs/REQUIREMENTS.md). Set explicitly to override.
+      '';
     };
 
+    kitty.enable = lib.mkEnableOption "Kitty with Nomarchy theming (palette/font/opacity from theme-state); also auto-on when nomarchy.terminal is kitty (OpenGL < 4.3 install fallback)";
+
     keyboard.layout = lib.mkOption {
       type = lib.types.str;
       default = config.nomarchy.settings.keyboard.layout or "us";