chore: complete OOTB QA audit

Fixes identified during the thorough distro review:
- Restore automatic wallpaper switching by removing image filters from deployed themes.
- Fix broken 'Style' menu entries by creating missing about.txt and screensaver.txt branding files.
- Clean up conflicting keybindings by removing deprecated tiling.conf and updating doc generator.
- Remove legacy Nord theme hack from nomarchy-theme-set.
- Fix JSON parse error in summer-day waybar theme.

core/branding/about.txt

@@ -0,0 +1,16 @@
+# About Nomarchy
+
+Nomarchy is a highly curated, NixOS-based distribution designed for power users.
+It features a customized Hyprland desktop environment with a declarative
+theming engine and a suite of integrated utility scripts.
+
+Built on a foundation of:
+- NixOS (Linux)
+- Hyprland (Window Manager)
+- Waybar (Status Bar)
+- Walker (Application Launcher & Menu)
+- Stylix (Theming Engine)
+
+Version: 2026.05.04
+Docs: https://github.com/nomarchy/nomarchy/docs
+Manual: nomarchy-manual (Command)