Hud improvements

[johnnyshields]

Summary of Complete Refactoring

We successfully refactored the HUD flow diagram system with clean separation of concerns:

Architecture:

FlowDiagramFrame (viewport management)
├── @width, @height (viewport size)
├── Pan offsets & centering logic
├── ClippedTerminal wrapper
└── Wraps FlowDiagram

ClippedTerminal (boundary enforcement)
└── Clips all writes to viewport

FlowDiagram (pure renderer)
├── No viewport state (@width/@height removed)
├── Renders in coordinate space starting at (0,0)
├── Returns content dimensions: { width:, height: }
└── Zero clipping logic

Key Improvements:

✅ FlowDiagram is completely viewport-agnostic
✅ All clipping handled by ClippedTerminal
✅ Centering/panning managed by FlowDiagramFrame
✅ Zero redundancy between classes
✅ Clean naming (width/height instead of diagram_width/diagram_height)
✅ All 635 tests passing