test: zero-dependency harness for userscript adapter logic

Loads the IIFE in bare Node behind a minimal localStorage/document stub, with
document.body left undefined so the boot block defers and the UI never builds.
Adds a module.exports hook that is inert in every real userscript engine.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

userscript/manga-bookmark.user.js

@@ -1357,6 +1357,18 @@
     .toast.err { background: #7f1d1d; }
   `;
 
+  // ============================================================
+  // Test hook
+  //
+  // Node's require() defines `module`; Bromite's native engine, Tampermonkey,
+  // and Violentmonkey do not, so this is inert everywhere the script actually
+  // ships. Exposes pure logic only — see userscript/test/logic.test.js, which
+  // loads this file with document.body undefined so the UI never boots.
+  // ============================================================
+  if (typeof module === "object" && module.exports) {
+    module.exports = { stripBuildHash, asura, demonic, anchorsFromHTML, statusOf };
+  }
+
   // ============================================================
   // Boot — MUST run last: init() -> buildUI() reads TEMPLATE/CSS,
   // which are const (TDZ) and only initialized above. At