[BUG] install-strategy=linked: workspace-only / undeclared workspaces are invisible to npm ls and npm query #9618

Part of #9608.

Is there an existing issue for this?

• I have searched the existing issues

This issue exists in the latest npm version

• I am using the latest npm

This is not just a request to bump a dependency for a CVE

• This is not solely a request to bump a dependency for a CVE

Current Behavior

Under install-strategy=linked, a declared workspace that is not also a root dependency is materialized on disk but is invisible to npm ls --all, npm ls --workspaces, and npm query ':root > *' (all return empty). The hoisted strategy lists every declared workspace.

Expected Behavior

All declared workspaces should be visible to npm ls (including --workspaces) and npm query under the linked strategy, matching the hoisted strategy.

Steps To Reproduce

cd "$(mktemp -d)"
echo 'install-strategy=linked' > .npmrc
echo '{ "name": "root", "version": "1.0.0", "workspaces": ["packages/*"] }' > package.json
mkdir -p packages/a packages/b
echo '{ "name": "a", "version": "1.0.0" }' > packages/a/package.json
echo '{ "name": "b", "version": "1.0.0" }' > packages/b/package.json
npm install >/dev/null
npm ls --workspaces        # linked: "(empty)";  hoisted: lists a and b
npm query ':root > *'      # linked: [];          hoisted: a, b

Environment

• npm: 12.0.0-pre.1 (latest)
• Node.js: v24.17.0
• OS Name: macOS (Darwin 25.5.0)
• System Model Name: MacBook (arm64)
• npm config:

install-strategy=linked