Set storeDir in every pnpm-workspace.yaml: `.pnpm-store` at the repo
root and `../.pnpm-store` in the ten module workspaces, so all of them
resolve to <repo>/.pnpm-store. pnpm resolves the value against the
workspace root, and nested workspaces do not inherit settings, which
had left the root workspace and the modules on two different stores.
Add scripts/clean-node-modules: removes every workspace node_modules
in one pass (ignores external/ and .opencode/), keeps the shared store
unless --store removes it too.
Verified: every workspace resolves the same store path; reinstalls
after a full clean reuse the cache with zero downloads;
frozen-lockfile installs pass in all 11 workspaces with no lockfile
changes; the frontend storybook suite stays green.
AI-assisted-by: omen-alpha
