refactor(modules): organize module tree

modules/desktop/apps/alacritty.nix

@@ -0,0 +1,18 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+# Alacritty as the desktop terminal.
+let
+  cfg = config.modules.desktop.apps.alacritty;
+  user = config.user.name;
+in
+{
+  options.modules.desktop.apps.alacritty.enable = lib.mkEnableOption "Alacritty as the desktop terminal";
+
+  config = lib.mkIf cfg.enable {
+    home-manager.users.${user}.home.packages = [ pkgs.alacritty ];
+  };
+}

modules/desktop/apps/firefox.nix

@@ -0,0 +1,129 @@
+{
+  config,
+  inputs,
+  lib,
+  pkgs,
+  ...
+}:
+# Firefox as the desktop browser: stock mainline, hardened and de-monetized by policy.
+let
+  cfg = config.modules.desktop.apps.firefox;
+  user = config.user.name;
+  firefoxAddons = inputs.firefox-addons.packages.${pkgs.stdenv.hostPlatform.system};
+in
+{
+  options.modules.desktop.apps.firefox.enable = lib.mkEnableOption "Firefox as the desktop browser";
+
+  config = lib.mkIf cfg.enable {
+    home-manager.users.${user} = hm: {
+      programs.firefox = {
+        enable = true;
+
+        # Enterprise policies: enforced and unchangeable from the browser UI.
+        policies = {
+          DisableTelemetry = true;
+          DisableFirefoxStudies = true;
+          DisablePocket = true;
+          OfferToSaveLogins = false;
+          DontCheckDefaultBrowser = true;
+          DisableFirefoxAccounts = true;
+
+          # Strip the monetized surfaces from the new-tab page.
+          FirefoxHome = {
+            SponsoredTopSites = false;
+            SponsoredPocket = false;
+            Snippets = false;
+          };
+        };
+
+        profiles.default = {
+          isDefault = true;
+
+          extensions = {
+            packages = with firefoxAddons; [
+              ublock-origin
+              proton-pass
+              sponsorblock
+            ];
+
+            # The Nord chrome theme is a declared extension setting, so home-manager
+            # owns the extension-settings store, overwriting runtime changes to it.
+            force = true;
+          };
+
+          # Stylix's Nord mapping paints the selected address-bar result a
+          # near-white grey, leaving its light text unreadable. Darken that one
+          # highlight to the Nord selection grey, from the same scheme.
+          extensions.settings."FirefoxColor@mozilla.com".settings.theme.colors.popup_highlight =
+            let
+              c = hm.config.lib.stylix.colors;
+            in
+            lib.mkForce {
+              r = c."base03-rgb-r";
+              g = c."base03-rgb-g";
+              b = c."base03-rgb-b";
+            };
+
+          settings = {
+            # Scale the UI and page by a fixed factor.
+            # Left at auto (-1), Firefox reads the panel's 1.5x and inflates its
+            # whole chrome while point-sized apps stay put.
+            # A shade under that brings it into line without dropping to true
+            # 1:1, which reads too small at this DPI.
+            "layout.css.devPixelsPerPx" = "1.25";
+
+            # Auto-enable the sideloaded Firefox Color add-on carrying the Nord
+            # chrome theme, which Firefox otherwise leaves disabled.
+            "extensions.autoDisableScopes" = 0;
+
+            # Sponsored surfaces the policies above do not reach.
+            "browser.urlbar.suggest.quicksuggest.sponsored" = false;
+            "browser.newtabpage.activity-stream.showSponsored" = false;
+            "browser.newtabpage.activity-stream.showSponsoredTopSites" = false;
+          };
+
+          search = {
+            # Declaring search overwrites Firefox's own engine list wholesale,
+            # so engines added later in the UI do not survive a rebuild.
+            force = true;
+            default = "ddg";
+
+            # The general-purpose commercial engines, hidden to leave a lean
+            # DuckDuckGo-and-Wikipedia list. They stay reachable through bangs.
+            # An engine carrying only metaData is treated as a builtin.
+            engines = {
+              google.metaData.hidden = true;
+              bing.metaData.hidden = true;
+              ebay.metaData.hidden = true;
+              "amazondotcom-us".metaData.hidden = true;
+            };
+            order = [ "ddg" ];
+          };
+        };
+      };
+
+      # Nord chrome for the one profile, applied through the Stylix-managed
+      # Firefox Color add-on that colorTheme enables.
+      stylix.targets.firefox = {
+        enable = true;
+        profileNames = [ "default" ];
+        colorTheme.enable = true;
+      };
+
+      # Links opened from other applications land in Firefox.
+      xdg.mimeApps = {
+        enable = true;
+        defaultApplications = {
+          "text/html" = "firefox.desktop";
+          "application/xhtml+xml" = "firefox.desktop";
+          "x-scheme-handler/http" = "firefox.desktop";
+          "x-scheme-handler/https" = "firefox.desktop";
+        };
+      };
+
+      # Firefox writes profiles.ini itself on first launch, so home-manager is
+      # told to own the file rather than fail activation refusing to clobber it.
+      home.file."${hm.config.programs.firefox.configPath}/profiles.ini".force = true;
+    };
+  };
+}

modules/desktop/apps/obsidian.nix

@@ -0,0 +1,18 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+# Obsidian as the desktop note-taking vault.
+let
+  cfg = config.modules.desktop.apps.obsidian;
+  user = config.user.name;
+in
+{
+  options.modules.desktop.apps.obsidian.enable = lib.mkEnableOption "Obsidian as the desktop note-taking vault";
+
+  config = lib.mkIf cfg.enable {
+    home-manager.users.${user}.home.packages = [ pkgs.obsidian ];
+  };
+}

modules/desktop/apps/steam.nix

@@ -0,0 +1,24 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+# Steam game launcher and runtime integration.
+let
+  cfg = config.modules.desktop.apps.steam;
+in
+{
+  options.modules.desktop.apps.steam.enable = lib.mkEnableOption "Steam game launcher";
+
+  config = lib.mkIf cfg.enable {
+    programs.steam = {
+      enable = true;
+      package = pkgs.steam.override {
+        extraEnv.STEAM_FORCE_DESKTOPUI_SCALING = "1.5";
+      };
+    };
+
+    hardware.steam-hardware.enable = true;
+  };
+}