What problem does this feature solve?

Currently, we have .rolldown/[build-id]/log.json which records the events during builds, but it doesn't have much information about the purpose of the build, among many other build-related info.

I propose to have a .rolldown/[build-id]/meta.json to store the basic information of the build, which can be retrieved easily and statically.

What does the proposed API look like?

I imagine the data format would look like:

interface RolldownBuildMeta {
  timestamp: string
  cwd: string // or root?
  options: RolldownOptions // serialized input, output, plugins, etc.
  mode: 'build' | 'dev'
  // ...
}