fix(workspaces): Use `shell` option on Windows in `execa` call (#11108)
## Summary
Addresses #11035 by adding `preferLocal` and `shell` options to `execa`
calls for package manager commands. This resolves the "no package.json
found" error that occurs when using Bun installed via bash installer on
Windows.
When Bun is installed via `curl -fsSL https://bun.sh/install | bash`,
it's placed in a Unix-style PATH that Node.js can't access without shell
context. Using `shell: true` on Windows allows the shell to resolve
these commands properly.
## Test Results
CI and canarying to be verified on Windows.
Co-authored-by: Claude <noreply@anthropic.com>