feat: enhance viewport handling on resize and panel transitions

[hugolytics]

Summary

Two related improvements to how the viewer handles viewport state when the layout changes.

1. Active-step viewport restoration on resize

When a resize event fires and a step is currently active, instead of trying to restore the previous raw pan/zoom values, re-apply the highlight and autoZoom for the current step nodes. This ensures highlighted elements stay properly framed after a resize rather than drifting to stale coordinates.

2. Viewport sync on panel CSS transition end

Adds an onPanelTransitionEnd listener on the panel element that fires onResize when the panel width or min-height CSS transition completes. This ensures the canvas and svg-pan-zoom instance are resized and re-centred after the panel slides open/closed. The listener is registered in mount() and cleaned up in destroy() to avoid leaks.

Files changed

• src/viewer/viewer.ts - active-step autozoom on resize; onPanelTransitionEnd handler lifecycle
• tests/viewer.test.ts - tests for current-step focus after resize, and panel transition end
• examples/vLLM/deployment.html / docs-site/public/examples/vllm/deployment.html - regenerated output