Fix zoom control: Initialize SVG viewBox on creation

Set viewBox attribute when SVG is created to match initial dimensions (100% zoom).
This prevents unexpected visual changes on first zoom control interaction.

Fixes issue where graph would jump/resize on first click of zoom slider even at 100%.

Co-authored-by: sei-vsarvepalli <[email protected]>

Author: Copilot

docs/ssvc-explorer/simple.js

@@ -131,6 +131,7 @@ const graphModule = (function() {
 	    .attr("class","mgraph")
 	    .attr("width", svg_width)
 	    .attr("height", svg_height)
+	    .attr("viewBox", "0 0 " + svg_width + " " + svg_height)
 	    .append("g")
 	    .attr("transform", default_translate)
 	    .attr("id","pgroup");