Repurpose the Maximize2 button in SchematicViewer as a fullscreen
toggle (was reset-zoom; percentage label is now clickable for that).
Add matching fullscreen toggle to WaveformViewer alongside the scope
button. Both use a shared useFullscreen hook for Escape-to-exit and
body scroll lock. In fullscreen mode, the SVG canvas and plot areas
fill the viewport with proper dimension tracking via ResizeObserver.
Ryan Malloy
2faa581e0b