Remove dead JS-bundling code from Bundle.php, drop updateGruntfile.php, make npm a hard install requirement

Bundle::all() has returned [] unconditionally since before this change (Grunt/terser
JS bundling was dropped when we moved to rollup), making its ~70-line body,
Bundle::urls(), and the bundle-cache lookup in js_includes() all unreachable.
Bundle::getImportMap() only did real work by looping over self::all(true), so it
too was provably always returning []; its Gruntfile.js regex-parsing (including a
now-nonexistent 'terser' config key) is removed along with it. js_includes() keeps
its per-file resolution (cache-buster, *.min.js companion lookup), which is the
only part that was ever doing anything.

updateGruntfile.php regenerated that dead 'terser' config and isn't wired into any
npm/composer/CI script; removed rather than fixed.

Gruntfile.js and build-css.mjs's doc-comments updated - Gruntfile.js is NOT dead,
build-css.mjs (npm run css) still reads its cssmin config directly, just no longer
via the grunt CLI.

install-cli.php previously let npm be missing and skipped `npm install`/`npm run
css`/`npm run build` with just a warning. Since CSS/JS bundling now requires npm
unconditionally (there's no longer a PHP-side fallback bundler), treat it like
php/git/composer: exit(1) if missing.

Author: ralfbecker

Gruntfile.js

@@ -12,14 +12,16 @@
  * grunt-contrib-cssmin vendor outdated, vulnerable glob/minimatch/js-yaml versions
  * with no upstream fix - see GHSA-mh99-v99m-4gvg and related advisories).
  *
- * This file is kept for two reasons:
- * - build-css.mjs (run via "npm run css") reads the cssmin config below through a
- *   minimal grunt.initConfig() shim, so the file lists stay a single source of truth
- * - Api\Framework\Bundle::getImportMap() (api/src/Framework/Bundle.php) parses this
- *   file's grunt.initConfig({...}) call directly by regex for (unrelated, legacy)
- *   JS bundle info
+ * This file is kept because build-css.mjs (run via "npm run css") reads the cssmin
+ * config below through a minimal grunt.initConfig() shim, so the file lists stay a
+ * single source of truth.
  *
- * Please use only double quotes, as we parse this file as json to update it!
+ * Api\Framework\Bundle::getImportMap() (api/src/Framework/Bundle.php) used to parse
+ * this file's grunt.initConfig({...}) call by regex for legacy JS bundle info, but
+ * that was JS bundling/minifying leftover from before rollup and has been removed -
+ * Bundle.php no longer reads this file at all.
+ *
+ * Please use only double quotes, as build-css.mjs parses this file as json.
  *
  * @param {object} grunt
  */