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.

agent/HARDWARE-QUEUE.md

@@ -436,12 +436,9 @@ the **T14s** (webcam case).
       **without** running `home-manager switch` by hand. **Fail** = still
       need the recovery one-liner, or GTK/nm-applet still wrong until a
       manual switch (then the bake is still incomplete).
-- [ ] **#95 themed Kitty fallback on Acer M5-481T** — after install from an
-      ISO that probes GL < 4.3 (or set `settings.terminal = "kitty"` +
-      `nomarchy-home`): SUPER+Return opens **Kitty** with Boreal (or current
-      theme) colors/font — not unthemed stock. `theme-state.json` should
-      show `"terminal": "kitty"`. Ghostty may still refuse if launched by
-      name (expected on HD 4000). XPS / modern-GL machines keep Ghostty.
+- [ ] **#95 Kitty-only terminal on Acer M5-481T** — after rebuild/install
+      from main: SUPER+Return opens **themed Kitty**; System › Doctor opens
+      a floating classed Kitty window. No Ghostty on PATH required.
 - [ ] **#124 flake pin after main-ISO install** — on a machine installed
       from a **main-built** ISO (post-fix): `~/.nomarchy/flake.nix`
       nomarchy input must not re-resolve to a lagging `v1` that lacks