- Add `sal-process` package for cross-platform process management.
- Update workspace members in `Cargo.toml`.
- Mark process package as complete in MONOREPO_CONVERSION_PLAN.md
- Remove license information from `mycelium` and `os` READMEs.
- Add a new `sal-os` package containing OS interaction utilities.
- Update workspace members to include the new package.
- Add README and basic usage examples for the new package.