Chapter dates: read date setting and tiered release dates (BL-0047)

- Chapter rows show when you first finished a chapter (setting: date + hour,
  date, off) from a new durable progress doneAt; older reads fall back to the
  reading clock's earliest remembered completion.
- chapter.json keeps added (arrival in this library, now kept on replace) plus
  x-dates.source (source upload, bulk imports flagged), x-dates.release
  (official, for a later metadata job) and x-dates.ecosystem (first entry into
  any Manga Circus library; carried over peering, earliest wins, clamped).
- Rows show one release date by tier: official > source upload > ecosystem >
  library, with all known dates in the tooltip (setting to hide).
- Fixes: WeebCentral dates came from the chapter page, which has none (every
  chapter got the download time); they now come from the full chapter list.
  MangaDex no longer writes a group's publishAt into added. Peering sends dates.
- tools/backfill-chapter-dates.js migrates an existing library (dry run default).
- Coverage dry run on the server: docs/chapter-dates-coverage-2026-10-24.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scraper/plugins/mangadex.js

@@ -1,6 +1,7 @@
 'use strict';
 
 const { specialKey } = require('../../chapter-identity');
+const { batchFlags } = require('../../chapter-dates');
 
 function localizedTitle(attributes = {}) {
   const titles = attributes.title || {};
@@ -41,14 +42,18 @@ function selectChapterReleases(resources = [], specialLabel = 'Special') {
     const prior = selected.get(number);
     if (!prior || compareRank(resource, prior) < 0) selected.set(number, resource);
   }
-  return [...selected.entries()].map(([number, resource]) => {
+  const chosen = [...selected.entries()];
+  const uploaded = chosen.map(([, resource]) => resource.attributes?.publishAt || resource.attributes?.readableAt || resource.attributes?.createdAt);
+  const batches = batchFlags(uploaded);
+  return chosen.map(([number, resource], index) => {
     const group = groupFor(resource);
     return {
       id: resource.id, number, title: resource.attributes?.title || '',
       ...(!chapterNumber(resource.attributes?.chapter) ? { special: true, label: specialLabel, sourceId: resource.id, sourceNumber: resource.attributes?.chapter ?? null } : {}),
       ...(resource.attributes?.volume ? { volume: chapterNumber(resource.attributes.volume) || String(resource.attributes.volume) } : {}),
       pages: Number(resource.attributes?.pages || 0),
-      added: resource.attributes?.publishAt || resource.attributes?.readableAt || resource.attributes?.createdAt,
+      // A group's upload time, not an official release; bulk uploads are flagged.
+      ...(uploaded[index] ? { uploadedAt: uploaded[index], uploadBatch: !!batches[index] } : {}),
       group,
       url: `https://mangadex.org/chapter/${resource.id}`,
     };

scraper/plugins/weebcentral.js

@@ -1,5 +1,6 @@
 'use strict';
 const { volumeKey } = require('../../chapter-identity');
+const { batchFlags } = require('../../chapter-dates');
 
 // First-party, pure parsing functions. This module never fetches remote content.
 const decode = value => value.replace(/&amp;/g, '&').replace(/&#39;/g, "'").replace(/&quot;/g, '"').replace(/<[^>]+>/g, '').trim();
@@ -21,19 +22,26 @@ function catalog({ html, url }) {
     const volume = !regular ? text.match(/^Volume\s+([0-9]+(?:\.[0-9]+)?)(?!\d)/i)?.[1] : null;
     const prologue = text.match(/Prologue(?:\s+([0-9]+))?/i)?.[1];
     const number = regular || (prologue ? `0.${prologue.padStart(2, '0')}` : /Prologue/i.test(text) ? '0' : null);
+    // The full chapter list carries each upload time; the chapter page itself has none.
+    const uploaded = match[3].match(/datetime="([^"]+)"/i)?.[1];
+    const uploadedAt = uploaded && Number.isFinite(Date.parse(uploaded)) ? uploaded : undefined;
     if (number) found.push({
       id: match[2], number, title: regular ? '' : `Prologue ${prologue || ''}`.trim(),
       ...(season ? { book: { number: season, title: `Season ${season}` } } : {}),
-      url: absolute(url, match[1]), raw: text,
+      url: absolute(url, match[1]), raw: text, ...(uploadedAt ? { uploadedAt } : {}),
     });
     else if (volume) found.push({
       id: match[2], number: volumeKey(match[2]), title: '', special: true,
       label: `Volume ${volume}`, releaseKind: 'volume', volume,
       book: { number: Number(volume), title: `Volume ${volume}` },
-      url: absolute(url, match[1]), raw: text,
+      url: absolute(url, match[1]), raw: text, ...(uploadedAt ? { uploadedAt } : {}),
     });
   }
   const chapters = [...new Map(found.map(chapter => [chapter.id, chapter])).values()];
+  // Back-catalog chapters were imported together; their upload time is not a release date.
+  batchFlags(chapters.map(chapter => chapter.uploadedAt)).forEach((batch, index) => {
+    if (batch !== null) chapters[index].uploadBatch = batch;
+  });
   const chapterLinks = [...html.matchAll(/<a\b[^>]*href="[^"]*\/chapters\/[A-Z0-9]+[^"]*"/gi)].length;
   return { chapters, chapterLinks };
 }
@@ -42,7 +50,6 @@ function chapter({ html, url }) {
   return {
     manifestUrl: html.match(/['"](https?:\/\/weebcentral\.com\/chapters\/[^'"]+\/images\?is_prev=[^'"]+)['"]/i)?.[1]
       || `${url}/images?is_prev=False`,
-    added: html.match(/datetime="([^"]+)"/i)?.[1],
   };
 }