fix(linker): hoist workspace deps from shared root

[timbrinded]

Summary

This updates the hoisted workspace linker so workspace member dependencies are planned against a shared workspace-root tree instead of independent per-importer trees.

In pnpm nodeLinker: hoisted workspaces, a non-conflicting dependency declared only by a workspace member can still be placed at the workspace root. Aube was placing those dependencies only under the member's own node_modules, which diverged from pnpm and made installs fragile when a root lifecycle script pruned member-local dependency trees.

Example

Setup:

pnpm-workspace.yaml

packages:
  - packages/*
nodeLinker: hoisted

package.json

  {
    "name": "root",
    "private": true,
    "packageManager": "pnpm@11.0.0",
    "scripts": {
      "postinstall": "node -e \"require('fs').rmSync('packages/app/node_modules',{recursive:true,force:true})\""
    }
  }

packages/app/package.json

  {
    "name": "app",
    "version": "1.0.0",
    "dependencies": {
      "@scope/scoped-dep": "file:../../vendor/scoped-dep"
    }
  }

Expected behaviour

openclaw builds

Actual behaviour

Caution

Building using nub run build fails with:

 ✘ [ERROR] Could not resolve "@pierre/diffs"

     extensions/diffs/src/viewer-client.ts:2:45:
       2 │ import { FileDiff, preloadHighlighter } from "@pierre/diffs";

1. node_modules/@scope/scoped-dep/index.js does not exist
2. packages/app/node_modules/@scope/scoped-dep is created during linking
3. packages/app/node_modules is then removed by root postinstall
4. require.resolve("@scope/scoped-dep", { paths: ["packages/app"] }) fails

Testing nub in the openclaw repo, @pierre/diffs was a valid dependency in the lockfile and showed up in nub why, but it was not resolvable after nub install. The package had only been installed under extensions/diffs/node_modules, and OpenClaw's root postinstall removes bundled plugin node_modules directories. pnpm avoids this by hoisting the non-conflicting dependency to the workspace root, where Node can still resolve it from the workspace member.