Handle noisy scanner POSTs without router action errors

[kentcdodds]

Summary

• patch the packaged workshop app after install so the root route returns a normal 405 for unsupported POSTs
• patch the packaged catch-all route so scanner/bot POSTs to unknown splat paths return a normal 404 instead of React Router's missing-action error
• keep existing real action routes and GET/HEAD routing behavior intact

Sentry

• Addresses epicshop issue EPICSHOP-F0 / 7447885629
• Targets noisy getInternalRouterError events from scanner POSTs such as /_rsc, /__nextjs_action, /RSC/...txt, /_middleware, /.action, /, /_next/image, and /__rsc

Validation

• npm run validate:all attempted, but the existing root script is not runnable because npm-run-all is not installed in the root lockfile
• npm run typecheck
• npm run lint
• node ./epicshop/test.js ..s
• Runtime production probes:
  • POST scanner/splat paths now return 404 without the did not provide an action router error text
  • POST / now returns 405 without the router error text
  • GET / remains 200, GET unknown paths remain 404, POST /progress remains 200
• GitHub PR checks are passing for Test and all Setup matrix jobs