fix(ci): switch typecheck action to stevearc/nvim-typecheck-action (#26)

Problem: mrcjkb/lua-typecheck-action runs lua-language-server in a bare
nix sandbox without neovim installed, causing 71 type errors for all
vim.* and uv.* types. LuaLS 3.17.x also introduced stricter type
checking that flags uv.aliases.fs_types mismatches not present in
3.16.4. The .luarc.json workspace.library entries conflicted with the
action's auto-appended luvit-meta, producing duplicate uv type unions.

Solution: switch to stevearc/nvim-typecheck-action@v2 (matching
upstream), pin LuaLS to 3.16.4, convert .luarc.json to nested format
without workspace.library (let the action provide VIMRUNTIME and
luvit-meta), and add .direnv/* to selene.toml exclude for local use.

.github/workflows/quality.yaml

@@ -62,12 +62,10 @@ jobs:
     if: ${{ needs.changes.outputs.lua == 'true' }}
     steps:
       - uses: actions/checkout@v4
-      - name: Run Lua LS Type Check
-        uses: mrcjkb/lua-typecheck-action@v0
+      - uses: stevearc/nvim-typecheck-action@v2
         with:
-          checklevel: Warning
-          directories: lua
-          configpath: .luarc.json
+          path: lua
+          luals-version: 3.16.4
 
   markdown-format:
     name: Markdown Format Check