refactor: group stow packages into common, mac and kde

Split the packages by platform so each app stays an opt-in Stow package
under common/, mac/ or kde/. KDE gets its own Fastfetch, Helium and
Spectacle packages, and darwin-breeze becomes kde/theme. The READMEs
document stowing a whole group as well as individual packages.

kde/spectacle/README.md

@@ -0,0 +1,28 @@
+# Spectacle
+
+Capture screenshots in the background, copy the image to the clipboard, and
+show a completion notification. Screenshots are not automatically saved.
+
+```sh
+stow -d kde -t "$HOME" spectacle
+./kde/spectacle/apply.py
+```
+
+Requires Spectacle, KDE Plasma 6, GNU Stow, Python 3, `kwriteconfig6`,
+`kbuildsycoca6`, `qdbus6`, and `gdbus`. Run the apply script in your KDE session.
+Move any existing files reported as conflicts by Stow out of the way first.
+
+- **Print** / **Meta+Shift+S**: select a rectangular region.
+- **Shift+Print**: entire desktop.
+- **Meta+Print**: active window.
+- **Meta+Shift+Print**: select a rectangular region.
+- **Meta+Ctrl+Print**: window under the cursor.
+
+The desktop launcher and shortcut entry are managed by Stow. The files in
+`settings/` are merged into `~/.config/spectaclerc` and `~/.config/klipperrc`
+by `apply.py`, preserving unrelated preferences and window state. Klipper's
+`SaveImages=true` keeps captured images available after Spectacle exits.
+
+After editing settings or launcher commands, run `apply.py` again. It rebuilds
+the cache using the KDE session's environment and reloads only Spectacle's
+shortcut component, preserving custom key bindings.