Implementation of Tab Completion & Keyboard Shortcuts

[Apurba-01]

This PR improves promptshell's input handling and terminal interaction for better cross-platform support.

• Enhanced main loop to support custom input methods and terminal clear commands (promptshell/main.py)
• Refactored readline setup for robust tab completion, history, and environment detection (promptshell/readline_setup.py)
• Improved modularity, maintainability, and user experience across platforms

issue #50
closes #50

[Apurba-01]

Please review and merge the pull request @Kirti-Rathi

[Kirti-Rathi]

The tab completions works fine but there's an issue, the first input is being ignored entirely, there's no confirmation prompt or execution. The expected behavior (confirmation followed by execution) only begins from the second input onward. This creates a confusing user experience, as it appears the first input does nothing. Attaching screenshot for reference. Kindly fix it and the implementation will be good to go.

[Apurba-01]

Sorry for the Issue withholds.... I will be fixing it as soon possible