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>

runtime/supervisor.js

@@ -3,7 +3,6 @@ const fs = require('fs'), path = require('path'), { spawn } = require('child_pro
 const SPECS = {
   reader: { script: 'server.js', port: () => process.env.PORT || 8080, file: () => path.join(process.env.DATA || 'data', 'runtime-reader.json') },
   scraper: { script: 'scraper/daemon.js', port: () => process.env.SCRAPER_PORT || 8091, file: () => path.join(process.env.SCRAPER_DATA || path.join(process.env.DATA || 'data', 'scraper'), 'runtime.json') },
-  sentinel: { script: 'sentinel/daemon.js', port: () => process.env.SENTINEL_PORT || 8092, file: () => path.join(process.env.SENTINEL_DATA || path.join(process.env.DATA || 'data', 'sentinel'), 'runtime.json') },
 };
 class Supervisor {
   constructor(name, options = {}) {