docs: plan the hyprland desktop epic (spec, ADR, tasks)

Add the hyprland-desktop spec, ADR 0003 recording the compositor choice
over Sway/KDE/niri, and the task breakdown (0021-0030) that decomposes
the desktop into granular grouped modules. Record the corrected host GPU
facts (zeus is AMD, raichu the sole Nvidia machine) in CLAUDE.md.

.claude/tasks/0022-stylix-nord-theming.md

@@ -0,0 +1,20 @@
+---
+spec: hyprland-desktop
+blocked-by: 0021-desktop-group-and-hyprland-session
+---
+
+## What to build
+
+Theme the whole new graphical layer Nord from a single source, and set the wallpaper.
+
+Add Stylix as a flake input and a desktop theming module that drives colors, system fonts, and cursor from one Nord base16 scheme across the graphical surface (GTK, Qt, and the compositor colors), plus a single static Nord wallpaper set by Stylix.
+Scope Stylix to the graphical layer only: leave its targets for the existing terminal tools (nvim, tmux, fish) off so their established hand-themes stand unchanged.
+The theming is reversible per target, so individual surfaces can migrate toward or away from manual theming later.
+
+## Acceptance criteria
+
+- [ ] Stylix is a flake input, wired into the host build.
+- [ ] A desktop theming module resolves a single Nord base16 scheme and applies it to GTK, Qt, cursor, and system fonts.
+- [ ] A single static Nord wallpaper is set by Stylix; no dynamic, animated, or cycling wallpaper.
+- [ ] Stylix targets for nvim, tmux, and fish are off, leaving their existing themes untouched.
+- [ ] neogaia builds green under `nix flake check`, and an eval probe confirms the resolved scheme is Nord.