feat: Add process package to monorepo

- 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.

process/src/lib.rs

@@ -0,0 +1,22 @@
+//! # SAL Process Package
+//! 
+//! The `sal-process` package provides functionality for managing and interacting with
+//! system processes across different platforms. It includes capabilities for:
+//! 
+//! - Running commands and scripts
+//! - Listing and filtering processes
+//! - Killing processes
+//! - Checking for command existence
+//! - Screen session management
+//! 
+//! This package is designed to work consistently across Windows, macOS, and Linux.
+
+mod run;
+mod mgmt;
+mod screen;
+
+pub mod rhai;
+
+pub use run::*;
+pub use mgmt::*;
+pub use screen::{new as new_screen, kill as kill_screen};