Reuse store content when restoring a remote build.
A remote side-effects restore downloaded every file of the artifact, then handed the bytes to the store, which addresses content by the very digest the artifact manifest already carries. A built package's files are mostly its own, and artifacts share files with one another, so most of what was transferred was content the store already had.
Ask the store first. `locateFileInStore` answers with the path it holds for a digest and mode, or nothing, and the restore only fetches what is missing. The store keeps executable and non-executable content apart, so the mode is part of the question.
Nothing is trusted that was not trusted before: the store addresses content by its hash, so a file it holds under an artifact's digest is that artifact's bytes.
The pacquet side already had the store helper this needs; its test pins the part that could silently drift — a digest or executable-bit rule diverging between the write side and the artifact side would not fail anything, it would just make the lookup always miss.
Follow-up to pnpm/pnpm#14171.
Zoltan Kochan
a83487c2f8