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>

peering/adapter.js

@@ -12,6 +12,7 @@ const { publishManifest } = require('../scraper/lib/publisher');
 const { writeJsonAtomic } = require('../scraper/lib/json-file');
 const { sleep } = require('../scraper/lib/delay');
 const { normalizeWorkIdentity, sameWorkIdentity, resolveWorkIdentity } = require('../scraper/lib/work-identity');
+const { fromPeer } = require('../chapter-dates');
 
 const dataRoot = () => path.resolve(process.env.PEER_DATA || path.join(process.env.DATA || 'data', 'peering'));
 const store = () => new PeeringState(dataRoot());
@@ -132,6 +133,8 @@ async function run(info, item, options) {
     }
     const publication = await publishManifest({ version: 1, series, chapters: [{
       number: ref.number, title: ref.title, book: { number: Number(ref.volume) || 1 },
+      // The peer's ecosystem date travels along: the chapter entered Circus there, not here.
+      dates: fromPeer(chapter.dates || ref.dates, peer.alias),
       source: { name: `Peer ${peer.alias} ${peer.id.slice(1, 7)}`, url: sourceUrl },
       pages: pages.map(page => ({ path: page.path })),
     }] }, { libraryRoot: options.libraryRoot, ...(manga ? { mangaDir: manga.path } : {}) });