chore(deps): bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v4...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/build.yml

@@ -41,7 +41,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
     - name: Install nix
       uses: cachix/install-nix-action@v31
       with:

flake.nix

@@ -19,7 +19,5 @@
           lib.filterAttrs
             (_: v: lib.isDerivation v)
             self.legacyPackages.${system});
-
-      overlays.default = import ./overlay.nix;
     };
 }

overlay.nix

@@ -7,6 +7,7 @@ let
   isReserved = n: n == "lib" || n == "overlays" || n == "modules";
   nameValuePair = n: v: { name = n; value = v; };
   nurAttrs = import ./default.nix { pkgs = super; };
+
 in
 builtins.listToAttrs
   (map (n: nameValuePair n nurAttrs.${n})

pkgs/iropke-batang/default.nix

@@ -1,30 +0,0 @@
-{ stdenvNoCC
-, fetchFromGitHub
-, lib
-}:
-
-stdenvNoCC.mkDerivation (finalAttrs: {
-  pname = "iropke-batang";
-  version = "1.2";
-  src = fetchFromGitHub {
-    owner = "iropke";
-    repo = "font-iropke-batang";
-    rev = "v${finalAttrs.version}";
-    hash = "sha256-wsu7JK0hHYn9aegaMeNV9fWvQ6KoMzHwOFWymWHYvxo=";
-  };
-
-  installPhase = ''
-    runHook preInstall
-    find . -type f -name '*.otf' \
-      -exec install -Dm644 {} -t $out/share/fonts/opentype \;
-    runHook postInstall
-  '';
-
-  meta = {
-    description = "Korean serif font";
-    homepage = "http://font.iropke.com/batang/";
-    changelog = "https://github.com/iropke/font-iropke-batang/releases";
-    license = lib.licenses.ofl;
-    platforms = lib.platforms.all;
-  };
-})

pkgs/quiver/default.nix

@@ -1,12 +1,4 @@
-{ stdenv
+{ stdenv, fetchNpmDeps, fetchFromGitHub, fetchzip, fetchurl, lib, imagemagick, nodejs_20 }:
-, fetchNpmDeps
-, fetchFromGitHub
-, fetchzip
-, fetchurl
-, lib
-, imagemagick
-, nodejs_20
-}:
 
 let
   vendoredKatex = fetchzip {
@@ -21,7 +13,7 @@ let
     url = "https://storage.googleapis.com/workbox-cdn/releases/7.0.0/workbox-window.prod.mjs.map";
     hash = "sha256-tUBiVoiKi3OCT+wctUYl0FVnT7StsGBDx7EzculcF5I=";
   };
-  rev = "1816fb788e4d315bf1dc30053a5e1646eb0af9b8";
+  rev = "9872f3f9265f92643387239e76042c8d3ffeb410";
 in stdenv.mkDerivation (final: {
   pname = "quiver";
   version = lib.substring 0 7 rev;
@@ -30,11 +22,11 @@ in stdenv.mkDerivation (final: {
     owner = "varkor";
     repo = "quiver";
     inherit rev;
-    hash = "sha256-29x2x0fLemkxhv+85wPnDrrlRW2h5qJtF/QTbGa6ghE=";
+    hash = "sha256-wSyCzUSLUL5nzUe5E4RdWv44WGd4C9WO6udkKY9cyBs=";
   };
   npmDeps = fetchNpmDeps {
     src = "${final.src}/service-worker";
-    hash = "sha256-1CdgZFvpyJFyh5x9ljTau6vrR7FeHRYZ1MG/ZOEoou8=";
+    hash = "sha256-xlww7Yfle58Qdwn/IcA6E6Fy7ZvH/ltKdlk6hvcC4UM=";
   };
   preBuild = ''
     cp -r $vendoredKatex src/KaTeX

pkgs/syd-plex-latex/default.nix

@@ -1,32 +0,0 @@
-{ stdenvNoCC
-, texlive
-}:
-
-stdenvNoCC.mkDerivation (final: {
-  pname = "syd-plex-latex";
-  version = "1.0.0";
-  src = ./.;
-  nativeBuildInputs = [ texlive.combined.scheme-small ];
-  passthru = {
-    pkgs = [ final.finalPackage ];
-    tlDeps = with texlive; [
-      plex
-      plex-otf
-      fontaxes
-      unicode-math
-      xetex
-      fontspec
-      xltxtra
-      realscripts
-      xecjk
-    ];
-    tlType = "run";
-  };
-  installPhase = ''
-    runHook preInstall
-    dir="$out/tex/latex/syd-plex"
-    mkdir -p "$dir"
-    mv syd-plex.sty "$dir"
-    runHook postInstall
-  '';
-})

pkgs/syd-plex-latex/syd-plex.sty

@@ -1,15 +0,0 @@
-\NeedsTeXFormat{LaTeX2e}
-\ProvidesPackage{syd-plex}[2025/12/01 Configure IBM Plex fonts]
-
-% Redefine some commands to make unicode-math work lol.  See §3.1 of the
-% unicode-math manual.
-\renewcommand*{\mathrm}[1]{\symup{#1}}
-
-\RequirePackage{plex-otf}
-\RequirePackage{xeCJK}
-\setmathfont{IBM Plex Math}
-\setmainfont{IBM Plex Serif}
-\setCJKmainfont{IBM Plex Sans KR}
-
-% Use sans-serif for \operatorname
-\setoperatorfont\mathsf