## Summary
- Add an optional browser-backed cover fetcher to the latest-chapter poller.
- Prefetch missing Kagane covers during the existing due-series cycle and persist them before a Reader opens the web UI.
- Keep chapter polling, cooldown stamping, and on-first-view fallback independent from cover failures.
## Behavior and safety
- Stored Kagane covers are detected before browser work, so later poll cycles do not refetch them.
- Nil cover fetchers and non-Kagane series retain the existing behavior.
- Shared Kagane image-id and content-type validation prevents challenge or non-image responses from poisoning persistent cover storage.
- The browser is wired into both the chapter and cover poller paths from the composition root.
## Verification
- `go test ./...`
- Focused latest, store, and web package tests
- Deterministic tests cover missing covers, cached covers, failed fetches, invalid content types, nil fetchers, and non-Kagane series.
Closes#45
Reviewed-on: #51
Co-authored-by: Sulthan Zaki <sultankiki05@gmail.com>
Co-committed-by: Sulthan Zaki <sultankiki05@gmail.com>
sulthan
d1800d0707