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.

docs/REQUIREMENTS.md

@@ -2,7 +2,7 @@
 
 What Nomarchy expects of a machine. This is a **living floor**, not a
 marketing sheet — numbers come from measured installs and known software
-floors (Ghostty, NixOS, the ISO). When a real machine pushes a bound, update
+floors (NixOS, the ISO, desktop GPU). When a real machine pushes a bound, update
 this file in the same change.
 
 Related: [HARDWARE.md](HARDWARE.md) (profiles/drivers),
@@ -22,39 +22,22 @@ Related: [HARDWARE.md](HARDWARE.md) (profiles/drivers),
 
 ## Graphics (default desktop)
 
-The default terminal is **Ghostty**, which requires **OpenGL 4.3** (desktop
-profile). That is a **GPU generation** limit, not a “driver not installed”
-problem:
+The sole terminal is **Kitty** (GPU-accelerated OpenGL, themed from
+theme-state). It runs on older integrated GPUs that reject Ghostty’s OpenGL
+**4.3** floor — notably **Intel HD 4000 / Ivy Bridge** (Acer Aspire M5-481T
+reported OpenGL **4.2** and could not start Ghostty). That is why Nomarchy
+standardized on Kitty only: one terminal to theme, one set of classed windows
+(doctor / calendar), no dual-stack or GL probe at install.
 
-| Generation (examples) | Typical max OpenGL (Mesa) | Default Ghostty |
-|-----------------------|---------------------------|-----------------|
-| Ivy Bridge / HD 4000 (e.g. **Acer Aspire M5-481T**, ~2012) | **4.2** | **Does not start** (`OpenGLOutdated`) |
-| Haswell and newer Intel iGPU, most AMD GCN+, discrete GPUs of the last decade | ≥ 4.3 | OK |
-| Dell XPS 9350 (Skylake) | ≥ 4.3 | OK (verified 2026-07) |
-
-**Why 4.2 and not 4.3 on HD 4000?** The silicon and Mesa’s feature set for
-that generation top out at OpenGL 4.2. No package upgrade on the distro can
-turn Ivy Bridge into a 4.3 device. Ghostty is choosing a modern GL baseline
-on purpose.
-
-**Install-time fallback (shipped):** when `nomarchy-install` can probe OpenGL
-(via `glxinfo` on the live session) and the version is **< 4.3**, it writes
-`settings.terminal = "kitty"` into the machine’s `theme-state.json`. Kitty is
-enabled and **themed from the same JSON** as Ghostty (palette, mono font,
-opacity). SUPER+Return then launches Kitty. Ghostty stays installed (doctor /
-calendar classed windows still call it — those helpers may still fail on old
-GL until a later follow-up).
-
-If the probe fails (no display / headless VM), Ghostty remains the default —
-do not guess. Existing installs can set the same by hand:
-
-```json
-"settings": { "terminal": "kitty" }
-```
-
-then `nomarchy-home` (or `home-manager switch`).
+| Generation (examples) | Notes |
+|-----------------------|--------|
+| Ivy Bridge / HD 4000 (~2012) | Supported with Kitty (verified path on Acer M5-481T) |
+| Haswell+ Intel, modern AMD, discrete GPUs | Supported |
+| SoftGL / virtio-gpu VMs | Hyprland needs GL for the session; Kitty is best-effort under softGL |
 
 Other Wayland clients vary; Hyprland itself is usually fine on these GPUs.
+A working GPU (or software GL for VMs) is still required for the desktop
+session — only the *terminal* no longer demands OpenGL 4.3.
 
 ---
 
@@ -154,8 +137,8 @@ Recovery menu. This requirements page only states why the disk fills up.
 
 | Machine | Role |
 |---------|------|
-| **Acer Aspire M5-481T** (~2012, Intel HD 4000, OpenGL 4.2) | Ghostty floor (#95); install bake / old-HW QA |
-| **Dell XPS 9350** (Skylake) | Install bake (#123); Ghostty OK |
+| **Acer Aspire M5-481T** (~2012, Intel HD 4000) | Old-HW QA; drove Kitty-only terminal (#95) |
+| **Dell XPS 9350** (Skylake) | Install bake (#123) |
 | AMD dev box / Latitude / T14s | Ongoing V3 (HARDWARE-QUEUE) |
 
 When you install on something older or smaller than the table, file what
@@ -167,7 +150,7 @@ broke in `agent/BACKLOG.md` and tighten this page.
 
 | Item | Topic |
 |------|--------|
-| BACKLOG **#95** | Ghostty fallback when OpenGL < 4.3 |
+| BACKLOG **#95** | Kitty as sole terminal (shipped) |
 | BACKLOG **#120** | Lighter netinstall ISO (download size ≠ installed size) |
 | BACKLOG **#123** | Installer HM pre-activate (first-boot polish) |
 | BACKLOG **#124** | Flake pin vs main/v1 lag after install |