docs: recommend install-strategy=linked to catch phantom dependencies

[manzoorwanijk]

Encourages package authors to develop under install-strategy=linked to surface undeclared ("phantom") dependencies before publishing.

Under the default hoisted node_modules, a package can import a dependency it never declared and still resolve it: a transitive dependency hoisted alongside it (or a workspace root's node_modules) happens to satisfy the import. That undeclared dependency passes the author's own build silently, then fails for a consumer who installs the package on its own. The linked (isolated) layout exposes only a package's declared dependencies, so such an import can fail at the author's build instead of shipping broken.

The change documents this in two places:

• The install-strategy entry in the config reference now recommends that authors use --install-strategy=linked during development, cross-linked to the developers guide.
• The Developers guide gains a "Catching undeclared ("phantom") dependencies" section under "Before Publishing", with a note that this is one check — a dependency satisfied by a devDependency or a workspace root's node_modules can still resolve locally — alongside auditing the dependencies the published package actually uses.

This is documentation-only; the config reference text is generated from the install-strategy definition description.

References

Closes #9675