feat: highlight same-net traces on hover

[fabicholas]

Summary

Closes tscircuit/tscircuit#1130

When hovering over a schematic trace, all traces that share the same electrical net are now highlighted in orange.

How it works

• Added useSchematicTraceHover hook (lib/hooks/useSchematicTraceHover.ts) that attaches mouseover/mouseleave listeners via event delegation on the SVG container div
• On hover, the hook reads data-subcircuit-connectivity-map-key from the hovered trace group to identify the net, then adds a trace-net-highlighted CSS class to all trace groups sharing that net key
• Falls back to highlighting just the hovered trace if no net key is present
• The highlight color (#e8a020 orange) is applied via CSS !important to override SVG presentation attributes on path elements (excluding the invisible hover outline) and circle.trace-junction elements
• The existing trace-invisible-hover-outline (8× stroke-width transparent path) provides a generous hit area for hover detection

Files changed

• lib/hooks/useSchematicTraceHover.ts — new hook
• lib/components/SchematicViewer.tsx — wires up the hook and injects the highlight CSS

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Project	Deployment	Actions	Updated (UTC)
schematic-viewer	Ready	Preview, Comment	May 20, 2026 3:20am