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/helium/.config/helium-browser-flags.conf

@@ -0,0 +1,6 @@
+# Hardware video acceleration (VA-API, AMD radeonsi) on Wayland
+--ozone-platform-hint=auto
+--enable-features=AcceleratedVideoDecodeLinuxGL,AcceleratedVideoDecodeLinuxZeroCopyGL,AcceleratedVideoEncoder
+
+# Darwin Breeze theme, generated by kde/theme/build.py
+--load-extension=~/.local/share/helium-themes/darwinbreeze

kde/helium/.gitignore

@@ -0,0 +1,2 @@
+# Helium caches the built theme next to the manifest.
+Cached Theme.pak

kde/helium/.local/share/helium-themes/darwinbreeze/manifest.json

@@ -0,0 +1,100 @@
+{
+  "manifest_version": 3,
+  "name": "Darwin Breeze",
+  "version": "1.0",
+  "description": "Generated by kde/theme/build.py from DarwinBreezeDark.colors",
+  "theme": {
+    "colors": {
+      "frame": [
+        35,
+        35,
+        35
+      ],
+      "frame_inactive": [
+        35,
+        35,
+        35
+      ],
+      "frame_incognito": [
+        35,
+        35,
+        35
+      ],
+      "frame_incognito_inactive": [
+        35,
+        35,
+        35
+      ],
+      "toolbar": [
+        35,
+        35,
+        35
+      ],
+      "background_tab": [
+        60,
+        60,
+        60
+      ],
+      "background_tab_inactive": [
+        60,
+        60,
+        60
+      ],
+      "tab_text": [
+        223,
+        223,
+        223
+      ],
+      "tab_background_text": [
+        223,
+        223,
+        223
+      ],
+      "tab_background_text_inactive": [
+        155,
+        155,
+        155
+      ],
+      "toolbar_text": [
+        223,
+        223,
+        223
+      ],
+      "toolbar_button_icon": [
+        223,
+        223,
+        223
+      ],
+      "bookmark_text": [
+        223,
+        223,
+        223
+      ],
+      "omnibox_background": [
+        24,
+        24,
+        24
+      ],
+      "omnibox_text": [
+        222,
+        222,
+        222
+      ],
+      "ntp_background": [
+        24,
+        24,
+        24
+      ],
+      "ntp_text": [
+        222,
+        222,
+        222
+      ],
+      "ntp_link": [
+        63,
+        157,
+        255
+      ]
+    }
+  }
+}

kde/helium/README.md

@@ -0,0 +1,11 @@
+# Helium
+
+Browser flags and the generated Darwin Breeze theme. From the repository root:
+
+```sh
+stow -d kde -t "$HOME" helium
+```
+
+The theme files are included, so the KDE `theme` package does not need to be
+stowed to use Helium's theme. To regenerate its colors from the shared color
+scheme, run `python3 kde/theme/build.py` and restart Helium.