Address review findings on the lnw pointer read (#89)

- Share one lnw host regex between matches and the pointer validator so
  the two cannot drift apart.
- Resolve the pointer href against the page address before validating,
  so a relative pointer still yields its Series instead of silently
  resolving to type other.
- Pin pointer/breadcrumb agreement on the divergent page and pin that a
  pointer off-host or not /novel/<slug>/ resolves to other.

userscript/novel-bookmark.user.js

@@ -132,26 +132,30 @@
     },
   };
 
+  // The host shape this adapter owns. One definition so the pointer validator
+  // and `matches` cannot drift apart (a leading subdomain is allowed).
+  const lnwHostRe = /(^|\.)lightnovelworld\.net$/;
+
   // A chapter page's pointer is its own link back to its Series. The href is
-  // page markup, so validate before trusting: the host must be this Site's (a
-  // leading subdomain is allowed, as in `matches`) and the path the
-  // /novel/<slug>/ Series shape. Anything else is not a pointer.
-  function seriesIdFromLnwPointer(href) {
+  // page markup, so validate before trusting: resolve it against the page
+  // address, require the host above and the /novel/<slug>/ Series path.
+  // Anything else is not a pointer.
+  function seriesIdFromLnwPointer(href, base) {
     if (!href) return null;
     let u;
     try {
-      u = new URL(href);
+      u = new URL(href, base);
     } catch (e) {
       return null;
     }
-    if (!/(^|\.)lightnovelworld\.net$/.test(u.hostname)) return null;
+    if (!lnwHostRe.test(u.hostname)) return null;
     const m = u.pathname.match(/^\/novel\/([^/]+)\/?$/);
     return m ? m[1] : null;
   }
 
   const lightnovelworld = {
     site: "lightnovelworld",
-    matches: (loc) => /(^|\.)lightnovelworld\.net$/.test(loc.hostname),
+    matches: (loc) => lnwHostRe.test(loc.hostname),
     detect(loc) {
       const path = loc.pathname;
       // /<slug>-chapter-<n>/ — flat, at the site root, not under /novel/. The
@@ -166,7 +170,7 @@
         // this replaced, not a safety net.
         const chapterSlug = m[1];
         const pointer = document.querySelector("a[aria-label='All Chapter']");
-        let seriesId = pointer ? seriesIdFromLnwPointer(pointer.getAttribute("href")) : null;
+        let seriesId = pointer ? seriesIdFromLnwPointer(pointer.getAttribute("href"), loc.href) : null;
         if (!seriesId) {
           // Fallback: the microdata breadcrumb's second crumb is the Series.
           // Scoped to the BreadcrumbList because itemprop="item" is not
@@ -174,7 +178,7 @@
           const crumb = document.querySelector(
             '[itemtype="http://schema.org/BreadcrumbList"] a[itemprop="item"][href*="/novel/"]'
           );
-          seriesId = crumb ? seriesIdFromLnwPointer(crumb.getAttribute("href")) : null;
+          seriesId = crumb ? seriesIdFromLnwPointer(crumb.getAttribute("href"), loc.href) : null;
         }
         // Neither pointer present, nor either pointing at a /novel/<slug>/
         // address on this host: not a page the script understands, so no