fix(arborist): surface undeclared workspaces under the linked strategy

[manzoorwanijk]

In continuation of our exploration of using install-strategy=linked in the Gutenberg monorepo, which powers the WordPress Block Editor.

Under install-strategy=linked, a declared workspace that the root does not depend on is installed on disk but was invisible to npm ls --all, npm ls --workspaces, and npm query ':root > *', all of which reported an empty tree. The hoisted strategy lists every workspace.

Undeclared workspaces are intentionally not symlinked into the root node_modules under the linked strategy, so when loadActual rebuilds the actual tree (from the filesystem scan or the hidden lockfile, neither of which records a node_modules/<ws> entry) the root's workspace edges resolve to nothing and the workspaces drop out of the tree that ls and query traverse. npm ls then hid those missing edges entirely to avoid a false UNMET DEPENDENCY.

The fix adds loadActual post-processing that, for the linked strategy, synthesizes an in-memory Link at node_modules/<ws> for each undeclared workspace so its root edge resolves, matching the logical layout the regular package-lock.json already records. This is introspection-only and writes nothing to disk. A declared workspace whose root link is genuinely missing is left alone so it still reports UNMET, an existing root child of the same name is never replaced, and a workspace that was not loaded is skipped. With the edges now resolving, the workspace-skip branch that npm ls used to suppress them is removed.

References

Fixes #9618

[manzoorwanijk]

@owlstronaut let us wrap this up. It may also need a manual backport.

EDIT: I am done for the day, please feel free to create a manual backport if needed, otherwise I will do it tomorrow.