Fold the sentinel into the scraper and drop the sentinel service (BL-0046)

The stall watchdog now runs inside the scraper (ScraperService.checkStalls,
every 30 s from the work loop): same rule as before, one checkpoint-safe
restart, quarantine on the second stall, missing checkpoint is no evidence,
and paused time no longer counts. Stalls are recorded as scraper incidents
(failure.kind 'stall'). The private /api/recovery endpoint is gone.

Dropped with the service: reader/scraper-unreachable incidents (supervisor
and Docker handle crashes; the health page shows "Scraper: unreachable"),
duplicate job-failure incidents and the unused /metrics endpoint.
The stack is now reader + scraper (+ optional peer-gateway).
The supervisor test moved to runtime/test (npm run test:runtime stays).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scraper/daemon.js

@@ -42,7 +42,6 @@ async function body(req) {
       if (url.pathname === '/api/queue/clear-completed') { const result = await service.clearCompleted(String(input.source || '')); return json(res, 200, { ...result, state: await service.publicState() }); }
       if (url.pathname === '/api/queue/reorder') { await service.reorder(input.ids); return json(res, 200, await service.publicState()); }
       if (url.pathname === '/api/control') { await service.control(String(input.action || ''), input.id); return json(res, 200, await service.publicState()); }
-      if (url.pathname === '/api/recovery') return json(res, 200, await service.recover(input));
       if (url.pathname === '/api/settings') { await service.updateSettings(input); return json(res, 200, await service.publicState()); }
       if (url.pathname === '/api/discovery/run') { await service.enqueueDiscoveryChecks('manual'); return json(res, 200, await service.publicState()); }
       if (url.pathname === '/api/library/auto-update') { await service.setMangaAutoUpdate(String(input.id || ''), !!input.enabled); return json(res, 200, await service.publicState()); }