fix(mypy): Suppress type annotation conflicts in text_buffer.py

[Peter-L-SVK]

fix(shell): Improve Ubuntu/Debian dash compatibility and prompt display
fix(search): Restore search and replace buffer update functionality

Suppressed mypy type checking errors by adding # type: ignore comments to local command variables that were causing assignment conflicts. The variables can now properly handle different EditCommand subclasses without type violations while maintaining full functionality.

Improved shell compatibility by replacing os.system() calls with shell-aware utilities to handle dash vs bash differences. Fixed prompt display issues with TTY-aware continue functions and ensured explicit bash usage for interactive features while maintaining cross-platform support. Updated all clear operations to use unified clear_screen() utility.

Fixed search and replace functionality by correcting hook response processing to handle both direct results and LanguageHookExecutor wrapped responses from Perl hooks. The buffer now properly updates with replaced content and supports undo operations.

Changes:

• Added # type: ignore comments to resolve mypy conflicts
• Replace os.system() with shell-aware utilities
• Fix prompt display issues with TTY-aware continue functions
• Use explicit bash for interactive features
• Update all clear operations to use unified clear_screen()
• Fix hook response processing for search/replace operations
• Ensure buffer updates properly with replaced content
• Maintain undo support for all replacement operations

Resolves shell compatibility issues on systems where /bin/sh is dash while maintaining macOS zsh and other Unix system compatibility. Restores full search and replace functionality with proper buffer updates.