build: use native Node TypeScript

[lewxdev]

summary

• run the custom server directly with Node.js 24.18.0 native TypeScript type stripping
• replace the TypeScript-only @/* alias with the package imports map #app/*
• use explicit .ts, .tsx, and index.ts specifiers so Node, TypeScript, and Next.js share one resolution source
• use native Node watch/start scripts and scope development watching to the server runtime graph
• move the custom entrypoint to server/ and refactor non-erasable parameter properties
• remove tsx plus its transitive esbuild packages
• leave Next.js responsible for compiling TSX

compatibility

The established #app/* form is intentional. Node.js 24.18.0 accepts the newer #/… form, but TypeScript 5.9.3 still rejects those specifiers. #app/* works in both.

Node's default dependency watcher also observes modules loaded and regenerated by Next.js, which caused restart loops during development. The script therefore uses --watch-path for server/ and app/utils/.

Node.js 24.18.0 documents --watch-path as macOS/Windows-only. Production Linux startup is unaffected, but Linux local development would require a future portable wrapper or a third-party watcher.

The latest main also has a pre-existing React ref type error at app/components/field.tsx:102. It is unchanged here to keep this PR narrowly scoped.

validation

• npm ci
• native import("#app/utils/game.ts") under Node.js 24.18.0
• npm run lint
• Prettier check across every changed file
• npm audit — 0 vulnerabilities
• git diff --check
• Redis-backed npm run dev — HTTP 200 with the package imports
• npx tsc --noEmit --incremental false — only the pre-existing React ref error above
• BASE_URL=http://localhost:3000 npm run build — webpack compiles the package imports successfully, then the unchanged React ref error blocks type checking
• temporary diagnostic correction of that unrelated annotation allowed the full production build to complete; the correction was reverted
• Redis-backed npm run start from that build — HTTP 200