Replace the scalar zoom prop with a {x,y,z} PanZoomState. The viewBox centre
is offset by the pan and width/height scaled by zoom; the default {0,0,1}
frames the whole tree (fit-to-screen). Page header buttons now step view.z
through clampZoom over the resolved 0.25–3.0 range.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>