fix: highlight same-net traces on hover

[minyanyi]

/claim tscircuit/tscircuit#1130
/fixes tscircuit/tscircuit#1130

Summary

Adds same-net hover highlighting for schematic traces in @tscircuit/schematic-viewer.

• Adds a focused useHighlightConnectedTracesOnHover hook.
• Groups schematic traces through source trace connectivity keys, connected source nets, and connected source ports.
• Applies hover metadata to both trace and trace-overlay SVG groups so every segment in the same net highlights together.
• Uses CSS :has() for hover state, avoiding per-mousemove React state updates.
• Adds unit coverage for same-net grouping and connected source-net fallback.

Test plan

• bun test
• bun run build
• git diff --check

Note: bun run build still reports the existing BaseManualEditEvent unused-import warning in lib/types/edit-events.ts, unrelated to this change.

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Project	Deployment	Actions	Updated (UTC)
schematic-viewer	Ready	Preview, Comment	May 11, 2026 4:51pm