chore(deps): upgrade pnpm to 12.2.1 (#1568)

## Description

Upgrade the workspace package-manager pin from pnpm 10.33.0 to pnpm 12.2.1 and record pnpm 12 native package-manager binaries in the lockfile. This adopts pnpm's Rust implementation without changing the application dependency graph.

## Type of Change

- [ ] 🚀 Feature (new functionality)
- [ ] 🐛 Bug fix (fixes an issue)
- [ ] 📚 Documentation (docs-only change)
- [x] 🔧 Maintenance (refactor, chore, CI, etc.)
- [ ] 🧪 Testing (test-only changes)

## Testing

- [x] Relevant checks pass locally (`pnpm run tsc`, `pnpm run lint`, `pnpm run test`)
- [ ] Added/updated tests for changes
- [x] Manually verified changes work as expected

Additional validation: `pnpm install --frozen-lockfile`, `pnpm run build`, and `pnpm run check` completed under pnpm 12.2.1; 235 test files and 5,740 tests passed.

## Checklist

- [x] Code follows project style (`pnpm run lint` passes for touched files)
- [x] Self-review completed
- [x] Documentation updated (not needed)
- [x] No new warnings introduced