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/adapters/weebcentral.js

@@ -4,6 +4,7 @@ const { SlowHttp } = require('../lib/http');
 const { fallbackDirection } = require('../../reading-direction');
 const parser = require('../plugins/weebcentral');
 const { parse } = require('../plugins/registry');
+const { sourceDate } = require('../../chapter-dates');
 
 function weebCentralInfo(value) {
   let url;
@@ -36,7 +37,8 @@ async function discoverWeebCatalog(seriesUrl, http) {
 
 async function discoverWeebChapter(chapter, http) {
   const pageHtml = await (await http.get(chapter.url, { accept: 'text/html' })).text();
-  const { manifestUrl, added } = parse('weebcentral', 'chapter', { html: pageHtml, url: chapter.url });
+  const { manifestUrl } = parse('weebcentral', 'chapter', { html: pageHtml, url: chapter.url });
+  const source = sourceDate(chapter.uploadedAt, 'WeebCentral', chapter.uploadBatch);
   const fragment = await (await http.get(`${manifestUrl}&reading_style=long_strip&current_page=1`, { accept: 'text/html' })).text();
   const parsed = parse('weebcentral', 'pages', { html: fragment, url: manifestUrl });
   const pages = parsed.pages.map(url => ({ url, headers: { referer: chapter.url } }));
@@ -46,7 +48,7 @@ async function discoverWeebChapter(chapter, http) {
     ...(chapter.special ? { special: true, label: chapter.label, sourceId: chapter.id,
       sourceNumber: chapter.volume, releaseKind: chapter.releaseKind, volume: chapter.volume } : {}),
     ...(chapter.book ? { book: chapter.book } : {}),
-    added,
+    ...(source ? { dates: { source } } : {}),
     source: { name: 'WeebCentral', url: chapter.url }, pages,
   };
 }