Check for PWA updates in long-lived sessions - #306

Closes #274

Summary

• poll ServiceWorkerRegistration.update() hourly so a standalone PWA discovers new deploys without navigation
• check again whenever the app returns to the visible state
• tie the interval and visibility listener to the existing abort lifecycle and keep failed checks silent
• preserve prompt-only activation so updates never reload underneath in-progress farm work
• add Vitest coverage for repeated polling, visibility checks, cleanup, rejected promises, synchronous throws, and test isolation
• refresh the graphify knowledge graph

The existing Help page and glossary already document background version discovery and prompt-before-reload behavior, so no user-facing terminology or copy change was needed.

Verification

• npm run test:coverage — 1,190/1,190 passed; coverage gates passed
• npm run build
• npm run verify:sw
• focused registerServiceWorker.test.ts — 22/22 passed
• git diff --check

Independent review

• Claude CLI: found three test gaps (repeated-period proof, synchronous-throw coverage, and cross-test lifecycle cleanup); all addressed before final verification
• separate Codex standards/spec review: no findings
• Pi v0.83.0 / DeepSeek V4 Flash DSpark final review: no findings