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.

docs/ROADMAP.md

@@ -404,6 +404,12 @@ Design/decision records and a running log of shipped work (items marked
   decision rather than a drive-by. Proved to fail: dropping snapshot makes it
   name the missing entry. **V3 pending** — that the apps *launch* needs real
   hardware (HARDWARE-QUEUE, Acer M5-481T).
+- ✓ **Kitty fallback when OpenGL < 4.3 (#95 partial):** Ghostty needs GL 4.3;
+  Ivy Bridge HD 4000 tops at 4.2 (Acer M5-481T). Installer probes `glxinfo`
+  and writes `settings.terminal = "kitty"` when below the floor; `kitty.nix`
+  themes Kitty from the same theme-state as Ghostty (ANSI, mono font,
+  opacity). Default machines stay Ghostty-only in the HM closure. V3 on Acer
+  still needed; doctor/calendar still invoke Ghostty by class.
 - ✓ **Mime defaults must name a present .desktop (#119):** same bug class as
   #94, one key over. `text/plain` pointed at `code.desktop` (vscode), which
   the live ISO never ships — GIO skips the missing entry and leaves no