fix(arborist): handle npm link with install-strategy=linked

[manzoorwanijk]

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

npm link is completely broken with install-strategy=linked.
Both npm link <path> and npm link <pkg> (via global) crash with ENOENT because the isolated reifier tries to extract the linked package into .store/ instead of symlinking it.

The root cause is that npm link creates a file: dependency pointing outside the project root.
The Link node ends up in idealTree.children (not fsChildren) because its path is root/node_modules/<name>.
The isolated reifier doesn't recognize it as a local dependency, so it routes it through #externalProxy which tries to extract it into the store.
The file: relative path then gets resolved from the store entry location instead of the project root, producing a wrong absolute path.

The fix detects Link nodes with file: resolved paths and treats them as workspace-like local dependencies.
Instead of extracting into .store/, they get symlinked directly in node_modules/, matching the behavior of the hoisted strategy.

References

Fixes #9166

[manzoorwanijk]

@wraithgar I am not sure why CI fails with npm error Cannot find module 'promise-retry'

[owlstronaut]

@wraithgar I am not sure why CI fails with npm error Cannot find module 'promise-retry'

don't worry about that, it is unrelated: nodejs/node#62425