v0.2.0 - Stable Cross Platform Shell

This release focuses on stability and cross-platform structure, not new shell features.

Highlights:

• Split command dispatch into a shared exec layer.
• Added a Windows execution backend and kept Unix execution support.
• Improved platform detection for Unix-like and Windows environments.
• Hardened input parsing and shell loop behavior for safer EOF and buffer handling.

Notes:

• Basic external command execution is supported on Unix and Windows.
• This is still a minimal shell, not a full cmd.exe or bash replacement.