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/BACKLOG.md

@@ -27,9 +27,9 @@ in [`docs/ROADMAP.md`](../docs/ROADMAP.md); map in
 ### Live ISO / install hardware findings — Acer Aspire M5-481T + Dell XPS 9350
 
 Bernardo, real installs 2026-07-13–14 (photos of the install end screens and
-post-boot sessions). Preserve separation: the installer bake failure, the
-flake pin, and the Ghostty GL floor are different root causes even when they
-show up on the same machine.
+post-boot sessions). Preserve separation: the installer bake failure and the
+flake pin are different root causes even when they show up on the same machine.
+(Terminal / Ghostty-on-Acer → shipped as Kitty-only, #95.)
 
 ### 123. Installer HM pre-activate aborts on dconf / missing XDG_RUNTIME_DIR
 
@@ -144,26 +144,6 @@ template source. Pass = Chromium launches after installation and HTTP/HTTPS
 mime defaults resolve to `chromium-browser.desktop` (and the intended live-ISO
 browser posture is explicit).
 
-### 95. Live ISO/install: Ghostty does not open on Acer (old GL) — **install fallback shipped**
-
-**Machine:** Acer Aspire M5-481T only (Intel HD 4000, OpenGL **4.2**). XPS
-starts Ghostty fine. Generation ceiling documented in `docs/REQUIREMENTS.md`.
-
-**Shipped (this iteration):** installer probes `glxinfo`; if OpenGL < 4.3,
-writes `settings.terminal = "kitty"` into theme-state. `modules/home/kitty.nix`
-installs and **themes** Kitty from the same palette/font/opacity as Ghostty.
-Default HM keeps Ghostty only (no kitty package). Manual override:
-`settings.terminal = "kitty"` or `nomarchy.terminal = "kitty"`.
-
-**Still open:**
-- **V3** on the Acer: fresh install (or hand-set terminal + `nomarchy-home`)
-  → SUPER+Return opens themed Kitty; Ghostty may still fail if launched by
-  name (expected).
-- Doctor / calendar classed windows still hardcode `ghostty` — may fail on
-  the same GL floor (separate small follow-up if they matter on old HW).
-- Live ISO session on HD 4000 still defaults to Ghostty until install (or a
-  live-side probe).
-
 ### 98. Boreal: button text renders black and is difficult to read
 
 Audit GTK button foreground/background contrast under Boreal, including the
@@ -222,7 +202,7 @@ a staircase.
 a real Nomarchy machine.** Chase the *fallback*, not one font's charset; this
 was got wrong twice while filing, both times by checking a single font:
 
-- The mono face is **per theme** (`ghostty.nix:22` → `t.fonts.mono` from the
+- The mono face is **per theme** (`kitty.nix` → `t.fonts.mono` from the
   theme JSON), not stylix's default. **Boreal — the default theme and the base
   state — is `GeistMono Nerd Font`**; the other 23 themes are `JetBrainsMono
   Nerd Font`. Any answer must hold for both.