fix: Nix 包固定 Electron 42

将 Nix 包运行时固定到 Electron 42，避免默认 Electron 43 的 KDE StatusNotifierItem 兼容问题。

AI-assisted-by: Codex
AI-model: gpt-5.6-sol
AI-reasoning-effort: medium
Co-authored-by: Codex <codex@openai.com>

packaging/nix/package.nix

@@ -4,7 +4,7 @@
 , nodejs
 , pnpm_11
 , pnpmConfigHook
-, electron
+, electron_42
 , cmake
 , pkg-config
 , makeWrapper
@@ -84,7 +84,7 @@ stdenv.mkDerivation (finalAttrs: {
       "$out/share/pixmaps/tama-asr.png"
 
     cmake --install build/fcitx5
-    makeWrapper ${electron}/bin/electron "$out/bin/tama-asr" \
+    makeWrapper ${electron_42}/bin/electron "$out/bin/tama-asr" \
       --add-flags "--ozone-platform=x11" \
       --add-flags "$appDir"