Idea: Distinguish between build-signature declarations and for-publication declarations

[amcasey]

Some declaration files are intended for publication and they need to be readable and "work" (e.g. no imports from node_modules). Others are, from a user's perspective, basically temporary files produced by the build to make subsequent builds more incremental (i.e. faster). Right now, we produce both sets of declaration files in the same way, but maybe we don't need to? As far as I can tell, the characteristics we require from "build" declarations are:

1. They change if-and-only-if the API of the underlying code changes
2. A source map can get you back from the declaration file to the input file

We can satisfy these requirements without, e.g.

1. Pretty-printing
2. Adding imports (as in Idea: Can declaration emit synthesize imports? #44044)
3. Confirming that referenced types are actually accessible (simplifying Idea: Can declaration emit synthesize type aliases? #44045)
4. Complaining about node_modules imports

One likely snag is how users will opt in to this behavior (Is it enough to be composite/incremental without having declarations? Is yet another switch required?).

[amcasey]

I think @andrewbranch has thought about some of this in the context of pnpm.

[amcasey]

This definitely overlaps with @sheetalkamat's recent work on signatures.