Node 22 leaves active LTS at the end of October. Move the Docker base
image and the documented local requirement to Node 24.
Pull @types/node from ^25 down to ^24 so the type definitions no longer
describe a newer runtime than the one in use. Types ahead of the runtime
let TypeScript accept APIs that are not there at execution time; the
opposite direction is harmless.
Add an engines field to record the supported version. No .nvmrc, since
the project is not used with a Node version manager.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
