refactor(wisdom): decentralize module defaults and update conventions

Move Home Manager module defaults from a centralized `desktop-home-defaults.nix`
file into their respective `wisdom` slices. This change aligns with the
updated documentation regarding module ownership, where defaults live
with the option that owns them rather than in a shared defaults file.

Additionally, update `docs/conventions.md` to reflect this new pattern for
defining `mkEnableOption` defaults and move base git/encryption
configurations into the core `wisdom` module.

- Delete `modules/hosts/desktop-home-defaults.nix`
- Update `modules/wisdom/default.nix` to include shared git and package defaults
- Add `default = ...` to `mkEnableOption` in various `wisdom` modules
- Update `docs/conventions.md` with new HM slice guidelines

modules/wisdom/browsers/chrome.nix

@@ -8,7 +8,9 @@
     {
       options.chiasson.home.browsers.chrome.enable = lib.mkEnableOption ''
         Chrome (unfree, needs `allowUnfree`); skipped if nixpkgs has no build for this platform.
-      '';
+      '' // {
+        default = false;
+      };
 
       config = lib.mkIf (root.enable && cfg.enable) {
         home.packages = lib.optional (

modules/wisdom/browsers/chromium-hevc.nix

@@ -155,13 +155,15 @@
           `failed Initialize()ing the frame pool` in Jellyfin.
 
           Requires `chiasson.system.chromiumHevc.enable` on NixOS.
-        '';
+        '' // {
+          default = true;
+        };
 
         packages = lib.mkOption {
           type = lib.types.listOf (
             lib.types.enum (lib.attrNames browserCatalog)
           );
-          default = [ "google-chrome" ];
+          default = if pkgs.stdenv.hostPlatform.isAarch64 then [ "chromium" ] else [ "google-chrome" ];
           description = "Chromium-based browsers to wrap.";
         };
 

modules/wisdom/browsers/edge.nix

@@ -6,7 +6,9 @@
       cfg = config.chiasson.home.browsers.edge;
     in
     {
-      options.chiasson.home.browsers.edge.enable = lib.mkEnableOption "Edge (unfree); skipped if unavailable on this platform.";
+      options.chiasson.home.browsers.edge.enable = lib.mkEnableOption "Edge (unfree); skipped if unavailable on this platform." // {
+        default = false;
+      };
 
       config = lib.mkIf (root.enable && cfg.enable) {
         home.packages = lib.optional (

modules/wisdom/browsers/flow.nix

@@ -56,7 +56,9 @@
     {
       options.chiasson.home.browsers.flow.enable = lib.mkEnableOption ''
         [Flow](https://github.com/MultiboxLabs/flow-browser) — upstream AppImage wrapped for NixOS.
-      '';
+      '' // {
+        default = false;
+      };
 
       config = lib.mkIf (root.enable && cfg.enable) {
         home.packages = lib.optional (

modules/wisdom/browsers/orion.nix

@@ -31,7 +31,9 @@
     {
       options.chiasson.home.browsers.orion.enable = lib.mkEnableOption ''
         [Orion](https://orionbrowser.com/) (Kagi) — installs the upstream Flatpak bundle and provides `oriongtk`.
-      '';
+      '' // {
+        default = false;
+      };
 
       config = lib.mkIf (root.enable && cfg.enable) {
         home.packages = [ oriongtk ];

modules/wisdom/browsers/zen.nix

@@ -8,7 +8,9 @@
     {
       imports = [ inputs.zen-browser.homeModules.beta ];
 
-      options.chiasson.home.browsers.zen.enable = lib.mkEnableOption "Zen Browser + locked-down policies / extensions.";
+      options.chiasson.home.browsers.zen.enable = lib.mkEnableOption "Zen Browser + locked-down policies / extensions." // {
+        default = false;
+      };
 
       config = lib.mkIf (root.enable && cfg.enable) {
         programs.zen-browser = {