enhancement: streamline command handling and enhance help output

[NamrathShetty]

This pull request improves the command-line interface of the mcp-publisher tool by adding enhanced help and usage messages for both global and command-specific contexts. It introduces structured help output for each command and refactors argument parsing for better clarity and maintainability.

Improvements to CLI help and usage:

• Added support for global --help, -h, help, --version, -v, and version flags, displaying usage or version information as appropriate.
• Introduced command-specific help output via a new printCommandHelp function, providing detailed usage, descriptions, options, and examples for each command (init, login, logout, publish).

Refactoring and maintainability:

• Refactored argument parsing by extracting the command and its arguments from os.Args, simplifying subsequent command handling and making the code more readable.
• Updated error messages and help prompts to use the extracted command variable, ensuring consistency in user feedback.

Motivation and Context

How Has This Been Tested?

Breaking Changes

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Documentation update

Checklist

• [x] I have read the MCP Documentation
• [x] My code follows the repository's style guidelines
• [x] New and existing tests pass locally
• [x] I have added appropriate error handling
• [ ] I have added or updated documentation as needed

Additional context

#735

This pull request improves the command-line interface of the mcp-publisher tool by enhancing how help and version information is handled and by adding detailed, command-specific help messages. The changes make the tool more user-friendly and provide clearer guidance for each command.

Improvements to CLI argument handling and help output:

• Refactored the main command parsing logic in cmd/publisher/main.go to handle global --help, -h, help, --version, -v, and version flags before dispatching to subcommands, ensuring consistent behavior and output for these flags.
• Added support for displaying command-specific help when --help, -h, or help is passed as the first argument to any subcommand, improving discoverability of command usage.

Addition of detailed command-specific help:

• Implemented a new printCommandHelp function in cmd/publisher/main.go that provides detailed usage, descriptions, options, and examples for each supported command (init, login, logout, publish), making it easier for users to understand and use each command correctly.