fix: restore same-net schematic trace hover grouping

[AlissonBecker1]

Summary

• derive schematic trace hover groups from trace geometry plus source/schematic port connectivity keys
• add subcircuit_connectivity_map_key to schematic traces before SVG conversion so the existing circuit-to-svg same-net hover CSS can apply
• add focused coverage for rendered traces, chained segments, disconnected same-net segments, and geometric fallback grouping
• add a small fixture for quick manual hover verification

Fixes tscircuit/tscircuit#1130

Verification

• bun test tests/connected-schematic-trace-groups.test.tsx
• bunx tsc --noEmit
• bun run build
• bunx biome check lib/components/SchematicViewer.tsx lib/utils/getConnectedSchematicTraceGroups.ts tests/connected-schematic-trace-groups.test.tsx examples/example21-connected-trace-hover.fixture.tsx
• git diff --check

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Project	Deployment	Actions	Updated (UTC)
schematic-viewer	Ready	Preview, Comment	May 22, 2026 8:16pm