Remove the client latest-chapter scan for lightnovelworld (#91) (#93)

Follows the spec published on #91: remove the client-side latest-chapter scan for lightnovelworld rather than porting #87's truncation into a second codebase.

- lightnovelworld.latestChapterFromAnchors deleted, not stubbed: absence is what the background-fetch guard keys off.
- computeLatestChapter tolerates an adapter with no scanner (yields null) and is exported as the test seam.
- backgroundRefreshLatest skips a scanner-less Site before the due filter: no Series page fetched, no freshness timestamp recorded, no batch slot consumed. The on-page path (maybeCaptureLatestOnSeriesPage) routes through the same null-tolerant computation.
- novelfull's scanner, the shared max-chapter helper and all four manga Sites untouched.
- userscript/AGENTS.md records the Poll-only contract for this Site and why.

All seven acceptance criteria from the spec met. node --check clean; novel suite 30/30 (the regression pin fails if a lnw scan is reintroduced, scoped or not); manga suite 35/35, manga userscript byte-for-byte unchanged.

Two-axis code review: no hard standard violations, spec-clean; one follow-up commit matching the sibling adapter guard from the manga script.

Reviewed-on: #93
Co-authored-by: Sulthan Zaki <sultankiki05@gmail.com>
Co-committed-by: Sulthan Zaki <sultankiki05@gmail.com>

userscript/novel-bookmark.user.js

@@ -218,12 +218,6 @@
       }
       return { type: "other" };
     },
-    latestChapterFromAnchors(anchors, seriesId) {
-      return maxChapter(
-        anchors,
-        new RegExp("lightnovelworld\\.net/" + escapeRe(seriesId) + "-chapter-([0-9.]+)/")
-      );
-    },
   };
 
   const ADAPTERS = [novelfull, lightnovelworld];
@@ -342,10 +336,11 @@
 
   // Highest chapter the site lists, or null when the markup yields nothing.
   // seriesId is only consulted by adapters whose pages carry other series'
-  // chapter links; the rest ignore it.
+  // chapter links. An adapter without a scanner (lightnovelworld — see the
+  // AGENTS.md entry) yields null, not an error.
   function computeLatestChapter(site, anchors, seriesId) {
     const a = adapterFor(site);
-    return a ? a.latestChapterFromAnchors(anchors, seriesId) : null;
+    return a && a.latestChapterFromAnchors ? a.latestChapterFromAnchors(anchors, seriesId) : null;
   }
 
   function currentSite() {
@@ -861,6 +856,14 @@
     const site = currentSite();
     if (!site) return;
 
+    // A Site with no client scanner (lightnovelworld) is refreshed by the Poll
+    // on a cooldown shorter than the client throttle; fetching its pages here
+    // would be a megabyte-scale request whose result is discarded. Skipping
+    // before the due filter records no freshness timestamp and consumes no
+    // per-navigation batch slot.
+    const adapter = adapterFor(site);
+    if (!adapter || !adapter.latestChapterFromAnchors) return;
+
     const checked = loadLastChecked();
     const now = Date.now();
     const due = state.list
@@ -871,7 +874,6 @@
       .slice(0, LATEST_CHECK_BATCH);
     if (due.length === 0) return;
 
-    const adapter = adapterFor(site);
     for (const bm of due) {
       // Recorded even when the fetch fails, so a broken series is retried on
       // the next throttle window rather than on every single page load.
@@ -1750,7 +1752,7 @@
   // Exposes pure logic only — see userscript/test/novel-logic.test.js.
   // ============================================================
   if (typeof window === "undefined" && typeof module === "object" && module.exports) {
-    module.exports = { novelfull, lightnovelworld, anchorsFromHTML, statusOf, kindOf, maxChapter, escapeRe, repairLnwStaleRow };
+    module.exports = { novelfull, lightnovelworld, anchorsFromHTML, statusOf, kindOf, maxChapter, escapeRe, computeLatestChapter, repairLnwStaleRow };
   }
 
   // ============================================================