docs: record conditional updated_at, latest-chapter tracking, favourites

Documents why updated_at moves only on reading progress and why PUT therefore
returns the stored row, why "latest chapter" is found from the browser rather
than the backend, and its limits — a bookmark is as current as its last check,
and nothing here can be instant.

Also corrects two stale claims: asurascans.com is the current domain, and
asuracomic.net deep links now 301 to its root rather than the matching path.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -34,13 +34,20 @@ Bromite userscript (isolated world, Shadow DOM UI, localStorage cache)
 | Method | Path | Auth | Description |
 |--------|------|------|-------------|
 | `GET` | `/bookmarks` | Bearer | All bookmarks (single-user). |
-| `PUT` | `/bookmarks/{key}` | Bearer | Upsert one series; server sets `updated_at`. |
+| `PUT` | `/bookmarks/{key}` | Bearer | Upsert one series; returns the row as stored. |
 | `DELETE` | `/bookmarks/{key}` | Bearer | Remove one. |
 | `GET` | `/healthz` | none | `200 ok`. |
 
 `key` is `<site>:<series_id>` — e.g. `asura:trash-of-the-counts-family-f886a8af`
 or `demonic:Infinite-Level-Up-in-Murim`. Sync is last-write-wins.
 
+`updated_at` orders the bookmark list, so it moves only on real reading
+progress: the server applies its timestamp when the row is new or
+`last_chapter_num` changes, and otherwise keeps the stored one. Favouriting a
+series or recording a newly published chapter therefore leaves the order alone.
+Because the timestamp a client sends is only a candidate, `PUT` echoes the row
+**as stored** and clients adopt that rather than their own payload.
+
 ### Develop / test
 
 ```bash
@@ -135,12 +142,42 @@ desktop for faster testing — install the same file unchanged.
   progress; unparseable numbers set the current chapter).
 - **Manual override**: panel → **Edit** on any row forces a specific chapter.
 - **Continue**: jumps to the last-read chapter (or the series page).
+- **Latest chapter**: rows read `Read: … · Latest: …` once the newest published
+  chapter is known and it is ahead of your progress. See below for how that is
+  found.
+- **Favourites**: the ☆ on any row toggles it; the **★ Favourites** tab narrows
+  the list. Favourited series still appear under **All**. The flag syncs, so it
+  follows you across devices; the chosen tab does not persist.
 - Bookmarks made on Asura appear when the panel is opened on Demonic, and vice
   versa — the backend is the shared store.
 
+Neither favouriting nor learning a new chapter reorders the list — only reading
+progress does.
+
 Offline / backend down: changes are cached in `localStorage` and retried on the
 next successful load (last-write-wins).
 
+#### How "latest chapter" is found
+
+Only a series page lists every chapter (a reader page links just its
+neighbours), and the backend cannot fetch either site — Cloudflare blocks
+server-side requests, and neither site offers an API or feed to poll. So the
+userscript does the looking, from your own browser session:
+
+- Opening a bookmarked series page records its newest chapter directly.
+- Otherwise it fetches series pages in the background — **same-origin only**, so
+  browsing Asura refreshes Asura bookmarks and Demonic refreshes Demonic. One
+  series per navigation, and at most one check per series every 4 hours
+  (`LATEST_CHECK_BATCH` / `LATEST_CHECK_THROTTLE_MS`). Failures are silent and
+  simply retried after the window.
+
+Freshness is tracked per device in `localStorage` under `mangabm:lastchecked`
+and is deliberately not synced, since each device checks on its own.
+
+This means a bookmark is as current as its last check — not the moment a
+chapter drops. Nothing can be instant here: neither site offers push, feeds, or
+an API.
+
 ---
 
 ## Adapter reference (verified live 2026-07-24)
@@ -150,10 +187,15 @@ The site adapters key everything off URL regex, with `title`/`cover` from
 
 | Site | Series URL | Chapter URL | `series_id` |
 |------|-----------|-------------|-------------|
-| **Asura** (`asurascans.com`; `asuracomic.net` 301s here) | `/comics/<slug-hash>` | `/comics/<slug-hash>/chapter/<n>` | `<slug-hash>` |
+| **Asura** (`asurascans.com`) | `/comics/<slug-hash>` | `/comics/<slug-hash>/chapter/<n>` | `<slug-hash>` |
 | **Demonic** (`demonicscans.org`) | `/manga/<slug>` | `/title/<slug>/chapter/<n>/<page>` (`chaptered.php?manga=<id>&chapter=<n>` 301s here) | `<slug>` |
 
 Notes:
+- **`asuracomic.net` deep links are dead (re-checked 2026-07-25).** They 301 to
+  the `asurascans.com` **root**, discarding the path, at the edge — before the
+  userscript gets a document — so nothing client-side can rescue them. Reach
+  series through `asurascans.com`. The host stays matched in case the redirect
+  starts preserving paths again.
 - Asura `og:title` carries a `Chapter N - Read Online \| Asura Scans` suffix that
   the adapter strips; Demonic chapter `og:title` is `<Title> Chapter N`.
 - Demonic's `<slug>` is identical on `/manga/…` and the canonical `/title/…`