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>

docker-compose.yml

@@ -57,7 +57,6 @@ services:
       READING_QUIZ_UNLOCK_MINUTES: ${READING_QUIZ_UNLOCK_MINUTES:-60}
       READING_QUIZ_CATALOG_PATH: ${READING_QUIZ_CATALOG_PATH:-}
       SCRAPER_URL: http://scraper:8091
-      SENTINEL_URL: http://sentinel:8092
       SCRAPER_TOKEN_FILE: /run/secrets/scraper_token
     networks: [backend, egress]
     healthcheck:
@@ -101,31 +100,6 @@ services:
       start_period: 60s
       retries: 3
 
-  sentinel:
-    <<: *app
-    command: [node, runtime/launch.js, sentinel]
-    volumes:
-      - type: bind
-        source: ${SENTINEL_DATA_PATH:-./data/sentinel}
-        target: /data/sentinel
-        bind: {create_host_path: false}
-    environment:
-      DATA: /data
-      SENTINEL_DATA: /data/sentinel
-      SENTINEL_HOST: 0.0.0.0
-      SENTINEL_PORT: "8092"
-      READER_URL: http://reader:8080
-      SCRAPER_URL: http://scraper:8091
-      SCRAPER_TOKEN_FILE: /run/secrets/scraper_token
-      TZ: ${TZ:-Europe/Berlin}
-    networks: [backend]
-    healthcheck:
-      test: [CMD, node, tools/healthcheck.js, sentinel]
-      interval: 30s
-      timeout: 5s
-      start_period: 60s
-      retries: 3
-
   peer-gateway:
     <<: *app
     profiles: [peering]