Handle large WeebCentral catalogs and correct MangaPill checkpoint monitoring

sentinel/monitor.js

@@ -36,6 +36,9 @@ class Monitor {
     const ids = new Set();
     for (const entry of scraper.active || []) {
       const id = entry.current.id; ids.add(id);
+      // Without a checkpoint, a null progress key stays constant forever and
+      // cannot prove a stall. Do not quarantine a live worker on that basis.
+      if (!entry.job) { this.observations.delete(id); this.resolve(`stall:${id}`); continue; }
       const key = progressKey(entry.job), prior = this.observations.get(id);
       if (!prior || prior.key !== key) { this.observations.set(id, { key, at: now }); this.resolve(`stall:${id}`); continue; }
       if (scraper.paused || scraper.sourcePaused?.[entry.source]) continue;