Launchers: apps' own desktop entries, rewritten; keyring moves into them

steamFrame.launchers.<desktop ID> takes the app's own entry (a Flatpak's
export, a Nix package's or a host file) and rewrites only its command lines
(hostEnv, env, flatpakArgs, args, wrappers) and the keys asked for
(mimeTypes, defaultFor, settings), so name, icon, translations and actions
stay the app's and follow its updates.

- Package entries are rewritten at build time; Flatpak/host file entries at
  runtime by steam-frame-nix-launchers into
  <session.runtimeDir>/steam-frame-nix/applications (tmpfs), on switch, at
  login and when Flatpak installs/updates apps (path unit); the Home Manager
  links point there.
- keyring.{enable,electron} replaces steamFrame.keyring.{flatpaks,programs}
  (clean break: the old options fail with the new form).
- Firefox's launcher is the Flatpak's entry with the profile wrapper in
  front (no --profile for the profile manager); Jellyfin's hardware
  decoding sets flatpakArgs and env.
- cleanup --all removes the tmpfs entries.
- Check on copies of the real Element, KRDC, Firefox, gedit, Jellyfin and
  Claude entries, quoting and generator behaviour.

flake.nix

@@ -34,13 +34,14 @@
       };
       firefox = ./modules/firefox.nix;
       jellyfin = ./modules/jellyfin.nix;
-      keyring = ./modules/keyring.nix;
+      launchers = ./modules/launchers.nix;
       docker = ./modules/docker.nix;
     };
     # Former attribute names, kept so existing imports keep working (not in
     # `default`, which imports each module once under its current name).
     aliases = {
       steam-keyboard-patch = modules.vr-keyboard-extra-keys;   # its name until 2026-09
+      keyring = modules.launchers;   # until 2026-09 (its options now fail with the new form)
     };
     systems = [ "aarch64-linux" "x86_64-linux" ];
     forSystems = f: nixpkgs.lib.genAttrs systems (system: f nixpkgs.legacyPackages.${system});
@@ -64,11 +65,12 @@
 
     # Tests of the VR keyboard (text model, corrector, swipe decoder on the
     # default German + English dictionary), the Jellyfin mpv shim, the
-    # Firefox launcher and install.sh cleanup: nix flake check
+    # Firefox wrapper, the launchers and install.sh cleanup: nix flake check
     checks = forSystems (pkgs: {
       cleanup = import ./modules/cleanup/check.nix { inherit pkgs; };
       firefox = import ./modules/firefox/check.nix { inherit pkgs; };
       jellyfin = import ./modules/jellyfin/check.nix { inherit pkgs; };
+      launchers = import ./modules/launchers/check.nix { inherit pkgs; };
       vr-keyboard = import ./modules/vr-keyboard/check.nix { inherit pkgs; };
     });