#90: repair stale lnw rows in place on the next chapter visit

A row keyed under the Chapter Slug its address was built from, while the
page pointer names a different Series, is stale. Rewrite its key, identity
and address in the cache, the retry-queue entry (if any) and the per-device
last-checked map together, then sync through the queue-backed path so an
offline repair parks and replays. Pure transform exported for the harness;
wired before render() at both detect() call sites. A row already under the
repaired key merges, keeping the farther-ahead progress, favourite OR'd and
the stronger lifecycle bucket.

userscript/novel-bookmark.user.js

@@ -244,6 +244,90 @@
     return ADAPTERS.find((a) => a.site === site) || null;
   }
 
+  // A stale lightnovelworld row is one keyed under the Chapter Slug its
+  // address was built from, while the page's pointer names a different
+  // Series. All three storage sites must move together: the cache row alone
+  // leaves a queued write replaying under a key whose row no longer exists
+  // (that write is silently lost), and a last-checked timestamp left behind
+  // re-fetches the repaired row on the next visit. A repair must never cost a
+  // Reader the chapter they were tracking, so when a row already holds the
+  // repaired key the two rows merge and the farther-ahead progress wins.
+  // Pure: no storage access, no module state, no clock.
+  function repairLnwStaleRow(list, queue, lastChecked, page) {
+    if (
+      !page ||
+      page.site !== "lightnovelworld" ||
+      !page.chapterSlug ||
+      !page.seriesId ||
+      page.chapterSlug === page.seriesId
+    ) {
+      return { list, queue, lastChecked };
+    }
+    const oldKey = "lightnovelworld:" + page.chapterSlug;
+    const newKey = "lightnovelworld:" + page.seriesId;
+    const stale = list.find((b) => b.key === oldKey);
+    if (!stale) return { list, queue, lastChecked };
+
+    let listOut;
+    const existing = list.find((b) => b.key === newKey);
+    if (existing) {
+      // Duplicate case (spec user story 2): one row must survive, and it is
+      // the one already under the repaired key — with the stale row's
+      // progress carried across when it is ahead, favourite OR'd, and the
+      // stronger lifecycle bucket kept (finished > archived > reading, so a
+      // merge can never silently un-archive or un-finish a row).
+      const merged = Object.assign({}, existing);
+      if (
+        existing.last_chapter_num == null ||
+        (stale.last_chapter_num != null && stale.last_chapter_num > existing.last_chapter_num)
+      ) {
+        merged.last_chapter = stale.last_chapter;
+        merged.last_chapter_num = stale.last_chapter_num;
+        merged.last_chapter_url = stale.last_chapter_url;
+      }
+      merged.favorite = !!(existing.favorite || stale.favorite);
+      const rank = (s) => ({ finished: 2, archived: 1, reading: 0 }[s || "reading"] || 0);
+      merged.status = rank(stale.status) > rank(existing.status) ? stale.status : existing.status;
+      merged.updated_at = Math.max(existing.updated_at || 0, stale.updated_at || 0);
+      listOut = list.filter((b) => b.key !== oldKey).map((b) => (b.key === newKey ? merged : b));
+    } else {
+      listOut = list.map((b) =>
+        b.key === oldKey
+          ? Object.assign({}, b, {
+              key: newKey,
+              series_id: page.seriesId,
+              series_url: page.seriesUrl,
+            })
+          : b
+      );
+    }
+
+    let queueOut = queue;
+    if (queue.some((e) => e.key === oldKey)) {
+      queueOut = queue
+        .map((e) => {
+          if (e.key !== oldKey) return e;
+          // An entry already under the repaired key wins: both markers read
+          // the same row from the cache at send time, so keeping both would
+          // replay one write twice.
+          if (queue.some((x) => x.key === newKey)) return null;
+          return Object.assign({}, e, { key: newKey });
+        })
+        .filter(Boolean);
+    }
+
+    let lastCheckedOut = lastChecked;
+    if (oldKey in lastChecked) {
+      lastCheckedOut = Object.assign({}, lastChecked);
+      // Max, not overwrite: a timestamp already under the repaired key must
+      // not be rolled back to an older one.
+      lastCheckedOut[newKey] = Math.max(lastCheckedOut[newKey] || 0, lastCheckedOut[oldKey]);
+      delete lastCheckedOut[oldKey];
+    }
+
+    return { list: listOut, queue: queueOut, lastChecked: lastCheckedOut };
+  }
+
   // 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.
@@ -1258,9 +1342,33 @@
     }
   }
 
+  // Runs the repair on every navigation, silently: rewrites a stale
+  // lightnovelworld row to the page's discovered identity, persists all three
+  // sites, and syncs through the queue-backed path so an offline repair parks
+  // and replays later. No toast — the Reader never asked for this. When the
+  // transform returns its inputs unchanged there is nothing to do.
+  function repairStaleLnwRow() {
+    const lastChecked = loadLastChecked();
+    const out = repairLnwStaleRow(state.list, queue, lastChecked, state.page);
+    if (out.list === state.list && out.queue === queue && out.lastChecked === lastChecked) return;
+    state.list = out.list;
+    reindex(); // byKey answers under the old key until rebuilt
+    saveCache(state.list);
+    queue.splice(0, queue.length, ...out.queue); // closures hold this array instance
+    saveQueue(queue);
+    saveLastChecked(out.lastChecked);
+    // Queue-backed sync, outcome swallowed: the repaired row is PUT (with its
+    // bucket when archived — the only status a userscript write may send) and
+    // the old server row is deleted so no duplicate survives on the wire.
+    const key = keyOf(state.page);
+    pushBookmark(key, statusOf(state.byKey[key]) === "archived").catch(() => {});
+    pushDelete("lightnovelworld:" + state.page.chapterSlug).catch(() => {});
+  }
+
   let lastUrl = location.href;
   function onNavigate() {
     state.page = detect();
+    repairStaleLnwRow();
     render();
     maybeAutoUpdate();
     maybeCaptureLatestOnSeriesPage();
@@ -1373,6 +1481,7 @@
   function init() {
     buildUI();
     state.page = detect();
+    repairStaleLnwRow();
     render();
     installNavWatcher();
     installLongPress();
@@ -1620,7 +1729,7 @@
   // 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 };
+    module.exports = { novelfull, lightnovelworld, anchorsFromHTML, statusOf, kindOf, maxChapter, escapeRe, repairLnwStaleRow };
   }
 
   // ============================================================