feat(sentry): add error monitoring for router, worker, and dashboard

[zbigniewsobiecki]

Summary

• Integrate @sentry/node v10 across all three container types (router, worker, dashboard) using Node's --import flag for early SDK initialization
• Add src/instrument.ts (module preload) and src/sentry.ts (thin no-op wrappers that guard all calls behind SENTRY_DSN)
• Wire Sentry captures into Hono error handlers, webhook processing, worker lifecycle, watchdog timeouts, queue errors, and retry exhaustion
• Forward SENTRY_* env vars from router to spawned worker containers

Bug fixes found during code review

#	Severity	Issue	Fix
1	High	tracesSampleRate=0 silently became 0.1 (|| treats 0 as falsy)	Use != null check on raw env var
2	High	Watchdog process.exit(1) dropped queued Sentry events (no flush)	Add await flush(3000) before exit
3	High	Router webhook try/catch swallowed queue failures (Redis down → HTTP 200)	Remove redundant try/catch, let errors propagate to app.onError → 500
4	Medium	Server mode handleProcessingError had no Sentry capture	Add captureException
5	Medium	Dashboard container had no Sentry setup at all	Add --import flag to Dockerfile + captures in error handler
6	Medium	server.ts error handler had no Sentry capture	Add captureException

Code quality

• Extract dispatchJob() from worker-entry.ts main() to fix cognitive complexity lint warning (17 → well under 15)
• Fix all import ordering and formatting issues flagged by biome

Files changed

New files: src/instrument.ts, src/sentry.ts, tests/unit/instrument.test.ts, tests/unit/sentry.test.ts

Modified (source): src/router/index.ts, src/router/worker-manager.ts, src/router/queue.ts, src/worker-entry.ts, src/agents/shared/lifecycle.ts, src/utils/lifecycle.ts, src/server.ts, src/server/webhookHandlers.ts, src/dashboard.ts, src/config/env.ts, src/config/retryConfig.ts, Dockerfile.dashboard, Dockerfile.router, Dockerfile.worker, CLAUDE.md

Modified (tests): tests/unit/utils/lifecycle.test.ts, tests/unit/server/webhookHandlers.test.ts

Test plan

• npm run lint — zero errors
• npm run typecheck — zero errors
• npm test — 2730 tests pass (165 files), including 22 new Sentry-specific tests
• CI passes (lint, typecheck, tests, Docker build validation)
• Manual: set SENTRY_TRACES_SAMPLE_RATE=0, verify tracing is disabled (not overridden to 0.1)
• Manual: deploy with SENTRY_DSN set, trigger a webhook error, verify event appears in Sentry

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