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>

server.js

@@ -39,7 +39,6 @@ const FULL_SCAN_MINUTES = +(process.env.FULL_SCAN_INTERVAL || 1440);
 const SECURE_COOKIE = process.env.COOKIE_SECURE === '1';
 const SCRAPER_URL = String(process.env.SCRAPER_URL || 'http://127.0.0.1:8091').replace(/\/$/, '');
 const SCRAPER_TOKEN = secret('SCRAPER_TOKEN');
-const SENTINEL_URL = String(process.env.SENTINEL_URL || 'http://127.0.0.1:8092').replace(/\/$/, '');
 const PEER_DATA = path.resolve(process.env.PEER_DATA || path.join(DATA, 'peering'));
 const peerStore = new PeeringState(PEER_DATA);
 const discoveryStore = new DiscoveryStore(DATA);
@@ -381,9 +380,7 @@ const routes = {
   },
   'GET /api/admin/health': async ({ u }) => {
     admin(u);
-    const sentinel = await fetch(SENTINEL_URL + '/api/state', { headers: SCRAPER_TOKEN ? { authorization: `Bearer ${SCRAPER_TOKEN}` } : {}, signal: AbortSignal.timeout(4000) })
-      .then(async r => { if (!r.ok) throw new Error(); return r.json(); }).catch(() => ({ status: 'unreachable' }));
-    return { reader: { ok: !scanState.error, uptime: Math.round(process.uptime()), scan: scanState }, sentinel, backup: backup.publicState() };
+    return { reader: { ok: !scanState.error, uptime: Math.round(process.uptime()), scan: scanState }, backup: backup.publicState() };
   },
   'GET /api/admin/backup': ({ u }) => { admin(u); return backup.publicState(); },
   'POST /api/admin/backup': ({ u, b }) => {