Provision JS checks with Nix

.gitea/workflows/check-js.yaml

@@ -10,10 +10,13 @@ jobs:
   typescript:
     name: Check TS (tsc)
     runs-on: nixos-x86_64-linux
+    defaults:
+      run:
+        shell: nix shell nixpkgs#nodejs_20 nixpkgs#yarn -c bash -e {0}
     steps:
       - uses: actions/checkout@v4
       - name: Install node_modules
-        uses: ./.github/actions/setup-node
+        run: yarn install --immutable --ignore-scripts
       - name: Check TypeScript
         run: yarn tsc
       - name: Test web HLS
@@ -22,10 +25,13 @@ jobs:
   lint:
     name: Lint JS (eslint, prettier)
     runs-on: nixos-x86_64-linux
+    defaults:
+      run:
+        shell: nix shell nixpkgs#nodejs_20 nixpkgs#yarn -c bash -e {0}
     steps:
       - uses: actions/checkout@v4
       - name: Install node_modules
-        uses: ./.github/actions/setup-node
+        run: yarn install --immutable --ignore-scripts
       - name: Run ESLint
         run: yarn lint
       - name: Verify auto-fix produces no changes