fix: highlight all traces on same net on hover

[rimi11e]

   Fixes tscircuit/tscircuit#1130

   ## Summary
   On hovering a schematic trace, every other trace electrically
   connected to the same net is now highlighted (orange, with a
   subtle drop-shadow). The grouping uses
   `getFullConnectivityMapFromCircuitJson`, the same connectivity
   utility tscircuit/circuit-json-to-readable-netlist relies on,
   so disjoint trace segments that share a port or a `source_net`
   are correctly grouped together.

   This addresses the review feedback on #149: "trace going to the
   right should also get highlighted as it is part of same net."

   ## What changed
   - `lib/hooks/useConnectedTracesHoverHighlighting.ts` (new): hook
     that memoizes a `schematic_trace_id → net group key` map per
     circuit-json change, and applies/removes a highlight CSS class
     on mouseover/mouseout.
   - `lib/components/SchematicViewer.tsx`: wires the hook in. Disabled
     while edit mode is active to avoid interfering with drag handles.
   - `package.json`: adds `circuit-json-to-connectivity-map` and
     `@tscircuit/soup-util` as dependencies.

   ## Notes
   - Listener is attached to the SVG container with `mouseover`/`mouseout`
     (event delegation), so it works regardless of how many traces are
     rendered.
   - Cleanup removes listeners and clears any active highlight on unmount
     or when `circuitJsonKey` changes.

   ## Testing
   - Verified visually with the existing cosmos examples (example1,
     example2, example4 multi-net circuits).
   - No existing snapshot/unit tests changed — purely additive.

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Project	Deployment	Actions	Updated (UTC)
schematic-viewer	Ready	Preview, Comment	May 17, 2026 10:15am