The imported module namespace — hosts read conventions like RESOLVER_PATHS off it.
True when StartupExport named a function and it was invoked by THIS call. False when the
entry has no startup export, the named export is missing, or the package was already loaded
earlier in this process (the module is still returned; the hook is not run twice).
OptionalWorkspacePresent only for 'manifest' entries: lets the loader fall back to importing the
workspace member by path when no resolution anchor can see it (pnpm strict layout).
A package the loader imported (and whose startup export, if any, it ran).