chore: delete defunct npm test command (#592)

## Overview

The test input files (`src/lib/_tests/`) were removed in 511c870 but
`bin/test.js` and the `test` script in `package.json` were left behind.
They ran against an empty directory and always produced an error.
Removed both. All testing is done manually.

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Wesley B <wesleyboar@users.noreply.github.com>

Author: wesleyboar

bin/test.js

@@ -28,7 +28,6 @@
     "prebuild:demo": "rm -rf dist/_utils && cp -r src/lib/_utils dist/_utils",
     "prestart": "npm run prebuild:demo",
     "build:demo": "fractal build",
-    "test": "bin/test.js && echo \"Test output at 'dist/_tests' (compare to test input)\"",
     "build:watch": "npm run build:css && touch src/lib/_imports/fractal.server.refresh.css",
     "watch": "npm-watch"
   },