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>

server.js

@@ -25,8 +25,9 @@ const peerClient = require('./peering/client');
 const { DiscoveryStore } = require('./discovery/store');
 const { generate: generateDiscovery } = require('./discovery/engine');
 const {
-  applyPulse, applyVisit, chapterInsight, eligiblePages, emptyRecord, libraryInsight, mangaInsight, publicSummary,
+  applyPulse, applyVisit, chapterInsight, earliestCompletion, eligiblePages, emptyRecord, libraryInsight, mangaInsight, publicSummary,
 } = require('./reading-analytics');
+const { chapterDates } = require('./chapter-dates');
 const { parseSchedule, publicSchedule, loadQuestionBank, createReadingAccess } = require('./reading-access');
 const { BackupService, BackupError } = require('./backup');
 
@@ -97,7 +98,7 @@ function checkPw(pw, stored) {
 }
 const DUMMY_HASH = hashPw('x');
 const DEFAULTS = { startMode: 'last', lastMode: 'page', adapt: true, skipExtras: false, skipCovers: false, flowPageGap: true, pageTone: 'original', readingClock: false, readingStory: true,
-  discoveryEnabled: false, discoveryReadingActivity: false, discoveryMature: false, zoom: {}, webhook: '' };
+  readDate: 'hour', releaseDate: true, discoveryEnabled: false, discoveryReadingActivity: false, discoveryMature: false, zoom: {}, webhook: '' };
 const settingsOf = u => ({ ...DEFAULTS, ...u.settings, zoom: { ...(u.settings && u.settings.zoom) } });
 
 function createUser(name, pw, admin, replace) {
@@ -322,6 +323,13 @@ function firstReleaseOf(meta) {
   }
   return { label: label || '', time: Number.isFinite(time) ? time : 0 };
 }
+// When a done chapter was completed: the progress record, or for reads saved before doneAt
+// existed, the earliest completion the reading clock still remembers.
+function readAtOf(progress, record) {
+  if (!progress || !progress.done) return null;
+  if (progress.doneAt) return { at: progress.doneAt, approx: false };
+  return earliestCompletion(record);
+}
 function continueOf(m, prog, s) {
   const ok = c => !(s.skipExtras && c.extra);
   let last = null;
@@ -437,7 +445,8 @@ const routes = {
     if (['last', 'flow', 'page', 'book'].includes(b.startMode)) s.startMode = b.startMode;
     if (['flow', 'page', 'book'].includes(b.lastMode)) s.lastMode = b.lastMode;
     if (['original', 'inverted', 'sepia', 'dim', 'extra-dim'].includes(b.pageTone)) s.pageTone = b.pageTone;
-    for (const k of ['adapt', 'skipExtras', 'skipCovers', 'flowPageGap', 'readingClock', 'readingStory',
+    if (['off', 'date', 'hour'].includes(b.readDate)) s.readDate = b.readDate;
+    for (const k of ['adapt', 'skipExtras', 'skipCovers', 'flowPageGap', 'readingClock', 'readingStory', 'releaseDate',
       'discoveryEnabled', 'discoveryReadingActivity', 'discoveryMature']) if (typeof b[k] === 'boolean') s[k] = b[k];
     if (b.zoom && typeof b.zoom === 'object') {
       s.zoom = {};
@@ -557,9 +566,10 @@ const routes = {
   },
 
   'GET /api/manga': ({ u, q }) => {
-    const m = mangaOf(q.get('m')), prog = progressOf(u, m), showStory = settingsOf(u).readingStory;
+    const m = mangaOf(q.get('m')), prog = progressOf(u, m), s = settingsOf(u), showStory = s.readingStory;
     const records = mangaReadingOf(u, m);
     return {
+      chapterDates: { read: s.readDate, release: s.releaseDate },
       id: m.id, title: m.title, meta: m.meta, cover: url(m.cover), direction: m.direction,
       collections: catalog.state.collections.filter(c => c.members.some(member => member.mangaId === m.id)).map(c => ({ id: c.id, title: c.title })),
       relations: catalog.state.relations.filter(r => r.state === 'confirmed' && (r.from === m.id || r.to === m.id)).map(r => ({ ...r,
@@ -569,6 +579,8 @@ const routes = {
       chapters: m.chapters.map(ch => ({
         id: ch.id, book: ch.book, label: ch.label, title: ch.title, extra: ch.extra, progress: prog[ch.id] || null, versions: versionsOf(m, ch, u),
         reading: showStory ? chapterInsight(records[ch.id]) : null,
+        readAt: s.readDate === 'off' ? null : readAtOf(prog[ch.id], records[ch.id]),
+        dates: s.releaseDate ? chapterDates(ch.versions) : null,
       })),
       reading: showStory ? mangaInsight(records, m.chapters.map(ch => ch.id)) : null,
       continue: continueOf(m, prog, settingsOf(u)),
@@ -637,8 +649,11 @@ const routes = {
   'POST /api/progress': ({ u, b }) => {
     const m = mangaOf(b.m), ch = chapterOf(m, b.c);
     const all = (db.progress[u.name] = db.progress[u.name] || {}), mp = (all[m.id] = all[m.id] || {}), old = mp[ch.id] || {};
+    const now = Date.now(), done = !!(old.done || b.done);
+    // doneAt: when the chapter was first completed; kept until it is marked unread.
+    const doneAt = old.done ? old.doneAt : done ? now : undefined;
     mp[ch.id] = {
-      v: String(b.v || ''), p: Math.max(0, b.p | 0), n: Math.max(0, b.n | 0), t: Date.now(), done: !!(old.done || b.done),
+      v: String(b.v || ''), p: Math.max(0, b.p | 0), n: Math.max(0, b.n | 0), t: now, done, ...(doneAt ? { doneAt } : {}),
       shift: Array.isArray(b.shift) ? b.shift.filter(Number.isInteger).slice(0, 1000) : old.shift || [],
     };
     save();