fv-go

Introduce `Buffer` text model for `Editor` widget with undo/redo, encoding support, and change listeners; Collapsing and paning feature. IDE feature showcase. Add tests for edge cases and grouped edits.

Fixed issues with and added regression tests for clipping, resizing, and redundant SIXEL emit behavior; refactor window and canvas floor logic

Add interactive "Game of Life" implementation with text and SIXEL render modes; include comprehensive tests for boundary modes and behavior

Improve cell size detection in terminal backends; add fallback mechanisms for TIOCGWINSZ and console font

Add extensive regression tests for rendering, focus behavior, and clamping across widgets; refactor edge case handling in `Editor`, `Splitter`, and `Terminal`