Highlight connected schematic traces on hover

[digzrow-coder]

Fixes tscircuit/tscircuit#1130.

Adds hover highlighting for schematic traces so every rendered trace segment on the same connected schematic net changes color together. The hook uses explicit schematic connectivity keys when available and falls back to grouping traces by shared edge endpoints.

Demo proof:

• Strong connected trace hover MP4: https://github.com/digzrow-coder/schematic-viewer/releases/download/pr-197-demo-20260514/pr-197-connected-trace-hover-strong-demo.mp4
• Strong connected trace hover GIF: https://github.com/digzrow-coder/schematic-viewer/releases/download/pr-197-demo-20260514/pr-197-connected-trace-hover-strong-demo.gif
• Strong contact sheet: https://github.com/digzrow-coder/schematic-viewer/releases/download/pr-197-demo-20260514/pr-197-strong-contact-sheet.jpg
• Original MP4: https://github.com/digzrow-coder/schematic-viewer/releases/download/pr-197-demo-20260514/pr-197-connected-trace-hover-demo.mp4

Validation:

• bun test tests/trace-net-key.test.ts
• bunx biome check lib/hooks/useHighlightConnectedSchematicTraces.ts tests/trace-net-key.test.ts
• bunx tsc --noEmit
• bun run build
• git diff --check
• Verified in Cosmos with Playwright that hovering one schematic trace marks both same-net traces as highlighted while unrelated traces stay unchanged.

/claim tscircuit/tscircuit#1130

AI-assisted with OpenAI Codex; I reviewed the diff, proof assets, and validation output before posting.

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Project	Deployment	Actions	Updated (UTC)
schematic-viewer	Ready	Preview, Comment	May 15, 2026 2:31am

[digzrow-coder]

Added actual interaction proof for the hover behavior: the demo moves onto one trace in the Cosmos fixture and shows the connected same-net trace highlighting with it while unrelated traces stay unchanged.

MP4: https://github.com/digzrow-coder/schematic-viewer/releases/download/pr-197-demo-20260514/pr-197-connected-trace-hover-demo.mp4
GIF: https://github.com/digzrow-coder/schematic-viewer/releases/download/pr-197-demo-20260514/pr-197-connected-trace-hover-demo.gif

[digzrow-coder]

Added stronger hover proof because the earlier recording was too subtle.

The new clip shows the cursor moving onto one schematic trace, both connected same-net segments turning orange together, and unrelated traces staying gray.

• Strong MP4: https://github.com/digzrow-coder/schematic-viewer/releases/download/pr-197-demo-20260514/pr-197-connected-trace-hover-strong-demo.mp4
• Strong GIF: https://github.com/digzrow-coder/schematic-viewer/releases/download/pr-197-demo-20260514/pr-197-connected-trace-hover-strong-demo.gif
• Contact sheet: https://github.com/digzrow-coder/schematic-viewer/releases/download/pr-197-demo-20260514/pr-197-strong-contact-sheet.jpg

[digzrow-coder]

Added focused automated coverage in 15a7ae7 for the same-net trace grouping used by the hover behavior. The new Bun test covers both explicit subcircuit_connectivity_map_key grouping and the shared-endpoint fallback path.

Validation rerun locally:

• bun test tests/trace-net-key.test.ts
• bunx biome check lib/hooks/useHighlightConnectedSchematicTraces.ts tests/trace-net-key.test.ts
• bunx tsc --noEmit
• bun run build
• git diff --check