Refactor waveform rendering from SVG to QPainter

[darktorres]

Description

Investigate whether the BeWavedDolphin waveform rendering can be made more efficient by replacing SVG-based rendering with direct QPainter drawing. SVG parsing and rendering has overhead that may be unnecessary for simple waveform shapes.

Acceptance Criteria

• Benchmark shows measurable performance improvement
• Visual quality is equal or better
• Code is simpler to maintain
• All existing waveform features preserved

Implementation Guide

1. Benchmark current performance

• Profile SignalDelegate::paint() with large waveforms (1000+ time steps)
• Measure SVG load time vs. draw time
• Identify if SVG rendering is actually the bottleneck

2. QPainter implementation

• Replace SVG pixmap rendering in SignalDelegate with direct QPainter calls
• Rising/falling edges: drawLine() calls with appropriate coordinates
• High/low levels: horizontal lines at fixed Y positions
• Transition markers: diagonal lines or X-crossings
• Use QPen styles for signal state (active=green, inactive=gray, unknown=yellow)

3. Caching strategy

• Cache rendered segments for stable signal regions
• Only re-render cells that changed between simulation steps

Key files

• App/BeWavedDolphin/SignalDelegate.h/.cpp — waveform cell rendering
• App/BeWavedDolphin/SignalModel.h/.cpp — signal data model
• App/BeWavedDolphin/WaveformView.h/.cpp — view widget