web: the ESLint layer ignores the vendored parser and fixtures

The flat config enumerated tests/vendor/acorn.mjs under an empty rule set;
an explicit ignore block keeps the second layer scoped to our own sources
and immune to a future default that warns on config-less files.

Co-authored-by: Ouroboros <311266734+ouroboros-agent@users.noreply.github.com>

web/eslint.config.js

@@ -21,6 +21,8 @@ const VENDORED_SCRIPT_GLOBALS = {
 };
 
 export default [
+    // The vendored parser the hermetic gate ships is not ours to lint.
+    { ignores: ['tests/vendor/**', 'tests/fixtures/**', 'node_modules/**'] },
     {
         // The ES modules the page loads.
         files: ['app.js', 'modules/**/*.js'],