h5i-nextjs-starter: a Next.js starter that runs from box create through export

[Koukyosyumei]

Part of #496.

A starter repository for Next.js, where the full loop works end to end: create a box, start the dev server, check it in the sandboxed browser, and export the result.

Estimated effort: 1 to 2 hours.

What to build

• A minimal Next.js app (npx create-next-app@latest is fine as a base).

• A checked-in .h5i/env.toml with the profile and the dev server declared, for example:

  [service.web]
  command = "npm run dev"
  port = 3000

• A README with copy-pasteable commands for the whole loop:

  h5i box create demo --profile agent-claude
  h5i box shell demo          # npm install && npm run dev inside the box
  h5i box view demo           # watch the page the box is serving
  h5i box share demo --port 3000   # optional: show it to someone else
  h5i box export demo         # patch.diff, report.md, receipt.json

• An open-source license.

Notes for whoever picks this up

• The point of this one is that every step works, not just create. If export or view needed a workaround, put the workaround in the README.
• [service.*] is supported at the workspace and process tiers. At supervised and container, run the dev server inside the same h5i box shell as everything else. State which tier you tested on.
• Next.js writes a lot into .next/ and node_modules/. Worth a line in the README about what that means for the exported patch, and a .gitignore that keeps the diff readable.
• Document the egress the build actually needs instead of telling people to open up the allowlist.
• Never ask users to copy credentials into the sandbox.

When you are done

1. Publish it as your own GitHub repository.
2. Open a PR adding it to SHOWCASE.md here.
3. A screenshot or terminal recording is welcome.

Please comment before starting so we can avoid duplicate work.