Reuse native Turbo builds in CI

[kostyafarber]

Summary

• stop TypeScript typechecking from building the Rust/N-API addon
• cache Turbo's native build record together with the .node artifact for unit tests
• let the unit-test graph build the addon once on a cache miss instead of running a separate build first

The previous native artifact cache restored the .node file, but Turbo had no cached task record and rebuilt it anyway.

Testing

• pnpm typecheck — passed without a native build task
• pnpm test:unit — passed
• Turbo typecheck dry-run contains zero shift-bridge#build tasks
• cached shift-bridge#build restored a deleted .node output in 38 ms
• repository pre-commit hooks