feat: Add dynamic generation mode switching to CLI chat interface

- Implement inline mode switching with --[mode] syntax
- Add parse_inline_mode() function with regex pattern matching
- Support for --stream, --chat, --batch, --simple mode overrides
- Include error handling for invalid mode specifications
- Add comprehensive test coverage for all mode switching scenarios
- Update help documentation and welcome messages
- Enhance CLI documentation with inline mode switching examples
- Maintain backward compatibility with existing CLI options
- Add visual feedback for mode overrides

Author: UtkarshTheDev