[FEAT] - Enhance CLI for GUI-less operations and scripting

[dylanlangston]

Is your feature request related to a problem? Please describe.

Currently, AvaloniaXKCD primarily operates as a GUI application. Users who want to retrieve comic information, integrate XKCD into scripts, or work from the terminal have limited options. The existing command-line interface is basic and could be significantly expanded.

Describe the solution you'd like

Expand command-line capabilities so users can interact with XKCD content directly from the terminal without launching the Avalonia GUI. The project already uses System.CommandLine for parsing arguments in https://github.com/dylanlangston/Axkcd/blob/master/src/AvaloniaXKCD/CommandLineParser.cs.

• Review existing CLI parsing logic and commands
• Extend CommandLineParser.cs to add new commands. Suggestions:
  • --get <comicNumber> or get-info — Retrieve and print comic title, alt text, date, and URL
  • --latest — Fetch and display the most recent comic
  • --random — Pull and display a random comic
  • --open <comicNumber> or open-browser — Launch specified comic in default web browser using Process.Start
• Format output cleanly for terminal display (support plain text and JSON modes for scripting)
• Integrate ExplainXKCD lookups (e.g., --explain <comicNumber>)
• Implement proper error handling and user feedback for invalid inputs or network issues
• Leverage XKCDCore
• Update README and add CLI usage documentation with examples
• Ensure cross-platform compatibility for all CLI commands

Describe alternatives you've considered

• Separate CLI-only tool, but integrating into main app reduces maintenance/distribution overhead.
• Basic --help only, but expanded commands provide real utility for power users.

Additional context

Acceptance Criteria:

• CLI mode can retrieve and display comics without launching GUI
• Commands are clearly described in --help output
• JSON output mode works for scripting/integration use cases
• All commands work cross-platform
• Error messages are helpful and actionable
• Documentation and examples are included in README
• CLI operations properly leverage existing XKCDCore logic

This makes AvaloniaXKCD useful for automation, shell integration, and users who prefer terminal interfaces.