feat: cable hover path highlighting

[ggfevans]

Parent Epic

Part of #71 (Network Interface Visualization and Connectivity)

Dependencies

• feat: Connection Graph Model - Phase 1: Port-Based Architecture #362 (Connection Graph Model) - data model must be complete
• feat: Port lookup indexes #370 (Port lookup indexes) - for efficient "connections for this port" queries
• spike: cable path rendering algorithm #262 (Connection path rendering)

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Summary

Highlight the full connection path when hovering over a port or connection.

Acceptance Criteria

• Hover port → highlight connections connected to that port
• Hover connection → highlight the connection path
• Show both endpoint ports highlighted
• Distinct highlight color (not selection color)
• Smooth transition animation
• Works across front/rear views

Highlight Styles

Element	Normal	Highlighted
Connection path	2px, cable color	3px, brighter, glow
Source port	Normal	Glow ring
Target port	Normal	Glow ring

Technical Notes

• Add hover state to connection SVG paths
• Add CSS transitions for smooth highlight
• May need to bring highlighted connection to top (z-order)
• Use feat: Port lookup indexes #370 (Port lookup indexes) for efficient queries

References

• Device42 cable highlighting