feat(nix): generate module options docs and sync to website

- Add nix/generate-hm-options.nix to export HM and NixOS module options as JSON via nixosOptionsDoc
- Expose hm-options-json and nixos-options-json packages in flake.nix
- Add CI workflow to auto-build and push JSONs to mangowm.github.io on module changes
- Add missing description to hm-modules enable option

.github/workflows/sync-nix-options.yml

@@ -0,0 +1,59 @@
+name: Sync Nix module options
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - nix/hm-modules.nix
+      - nix/nixos-modules.nix
+      - nix/generate-options.nix
+      - flake.nix
+      - flake.lock
+
+concurrency:
+  group: sync-nix-options
+  cancel-in-progress: true
+
+jobs:
+  sync-nix-options:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+
+      - uses: cachix/install-nix-action@v30
+        with:
+          extra_nix_config: |
+            experimental-features = nix-command flakes
+
+      - name: Build options JSONs
+        run: |
+          HM_OUT=$(nix build .#hm-options-json --no-link --print-out-paths)
+          NIXOS_OUT=$(nix build .#nixos-options-json --no-link --print-out-paths)
+          cp "$HM_OUT/share/doc/nixos/options.json" /tmp/hm-options.json
+          cp "$NIXOS_OUT/share/doc/nixos/options.json" /tmp/nixos-options.json
+
+      - name: Checkout website
+        uses: actions/checkout@v4
+        with:
+          repository: mangowm/mangowm.github.io
+          path: website
+          token: ${{ secrets.WEBSITE_SYNC_TOKEN }}
+          fetch-depth: 1
+
+      - name: Copy JSONs to website
+        run: |
+          cp /tmp/hm-options.json website/apps/web/src/hm-options.json
+          cp /tmp/nixos-options.json website/apps/web/src/nixos-options.json
+
+      - name: Commit and push
+        working-directory: website
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+          git add apps/web/src/hm-options.json apps/web/src/nixos-options.json
+          git diff --staged --quiet || git commit \
+            -m "nix: update module options JSON" \
+            -m "${{ github.server_url }}/${{ github.repository }}/commit/${{ github.sha }}"
+          git push