Update IDETemplateMacros.plist and replace headers in 136 Swift files with
new format: 🖥️ TUIKit — Terminal UI Kit for Swift. Remove sdsd.swift template draft.
Introduce FrameDiffWriter that stores the previous frame's output and
compares line-by-line on each render. Only lines that actually differ
are written to the terminal, reducing I/O by ~94% for mostly-static UI.
- Extract output line building from WindowGroup.renderScene into
FrameDiffWriter.buildOutputLines() pure function
- WindowGroup.renderScene now returns FrameBuffer instead of writing
directly to terminal
- RenderLoop (now final class) owns FrameDiffWriter for state tracking
- Content and status bar are diffed independently
- SIGWINCH invalidates diff cache for full repaint on resize
- SignalManager gains separate consumeResizeFlag() for resize detection
- 13 new tests for diff computation and output line building