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/0028-screenshot-capture.md

@@ -0,0 +1,19 @@
+---
+spec: hyprland-desktop
+blocked-by: 0021-desktop-group-and-hyprland-session
+---
+
+## What to build
+
+Keyboard-driven screenshots that open in an annotation editor by default and land in both the clipboard and a file.
+
+Add a screenshot module to the desktop group, enabled through the aggregator, using grim and slurp wrapped by grimblast and routed through the satty annotation editor so annotation is the default.
+Cover region, active-window, and full-screen captures, each exporting to both the clipboard and a file.
+Bind region on `Super+L`, active window on `Super+Shift+L`, and full screen on `Super+Ctrl+L`.
+
+## Acceptance criteria
+
+- [ ] A screenshot module exists in the desktop group and is enabled by the aggregator.
+- [ ] Region, active-window, and full-screen captures work, each opening in satty and exporting to both clipboard and file.
+- [ ] Captures are bound on `Super+L`, `Super+Shift+L`, and `Super+Ctrl+L`.
+- [ ] neogaia builds green under `nix flake check`.