test: Add lockfile fixture for pnpm v9 injected workspace deps (issue #8243) (#12082)
## Summary
- Adds an end-to-end lockfile fixture (`pnpm-v9-inject-workspace`) that
reproduces the scenario from #8243: `turbo prune` with pnpm v9 lockfiles
using `dependenciesMeta.injected: true` and `link:` protocol resolution
- Adds a Rust unit test (`test_subgraph_with_pnpm9_link_injected_deps`)
covering the `link:` protocol case specifically, since the existing
injected-dep tests only covered `file:` protocol
The underlying bug was already fixed in #12073. The existing tests for
injected deps only exercised the `file:` protocol (used by pnpm 10's
`injectWorkspacePackages: true`). In pnpm 9, `dependenciesMeta.injected:
true` still resolves to `link:` in the lockfile, which is a distinct
code path. This adds regression coverage for that case.
Closes #8243