feat: highlight all same-net traces on hover

[makaiachildress-web]

Summary

• Adds useTraceHoverHighlight hook that highlights all traces in the same net when hovering over any trace
• Net grouping uses subcircuit_connectivity_map_key (primary) with BFS over shared connected_source_port_ids as fallback
• Disables the default per-trace :hover CSS from circuit-to-svg to prevent double highlighting
• Uses precomputed group keys to eliminate flicker when moving between traces in the same net

Fixes tscircuit/tscircuit#1130
/claim #1130

How it works

1. On mount, buildNetGroups() precomputes net membership for every schematic trace:
   • Strategy 1: Groups traces sharing the same subcircuit_connectivity_map_key
   • Strategy 2: For traces without the key, BFS walks source_trace -> connected_source_port_ids to find all source traces on the same net, then maps back to schematic trace IDs
2. Each trace gets a stable group key for O(1) pointer-move comparisons
3. On pointermove, finds the hovered trace via Element.closest(), looks up its net group, and sets stroke to #1e90ff on all paths in that group
4. On pointerleave, restores original stroke colors
5. Injected CSS override disables the default .trace:hover { filter: invert(1) } and the :has()-based net hover rules from circuit-to-svg

Test plan

• Hover over a trace -> it turns blue (#1e90ff)
• Other traces on the same net also highlight
• Moving pointer off the trace restores original colors
• Moving between traces on the same net does not flicker
• No interference with existing component drag/dash animation
• Works with the MrPicklePinosaur/tscircuit_demo circuit

Files changed

• lib/hooks/useTraceHoverHighlight.ts - New hook with net grouping and hover logic
• lib/components/SchematicViewer.tsx - Import and call the hook

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Project	Deployment	Actions	Updated (UTC)
schematic-viewer	Ready	Preview, Comment	Feb 17, 2026 7:40pm