Reorganize Firefox configuration and repository documentation

- Configure Firefox with privacy settings and extensions (Bitwarden, Plasma Integration, MetaMask, Kagi Search, uBlock Origin)
- Set Kagi as default/only search engine
- Add MOZ_USE_XINPUT2=1 for smooth scrolling
- Create context/ directory for concise unit documentation
- Create tests/ directory for test scripts
- Move test-firefox-config.sh to tests/
- Update agents.md with documentation workflow guidelines
- Fix syntax errors in desktop.nix and dev.nix

systems/desktop.nix

@@ -1,5 +1,5 @@
 { config, pkgs, ... }:
-
+{
   services.pipewire = {
     enable = true;
     alsa.enable = true;