946: Distance-based node collapsing for 2D Network View

[glstott]

This addresses enhancement #946.

Summary

• Adds distance-based node collapsing to the 2D Network view.
• Adds a new “Collapse Related Nodes” settings panel with:
  • Enable/disable toggle
  • Distance threshold slider/input
  • Metric-aware labels and steps for TN93 percentage, TN93 decimal, and SNPs
• Collapses threshold-connected distance components into aggregate nodes.
• Scales aggregate nodes by member count.
• Renders multi-category aggregate nodes as pie charts using node color groups.
• Drops internal/self links created by collapsed members and retargets external links to aggregate nodes.
• Adds aggregate-node tooltips with Bubble-style tables showing:
  • Category counts
  • Percentages
  • Total node count
  • Mean internal distance
• Adds a warning when collapse is enabled while non-circle node shapes are active, since collapsed nodes render as circles.
• Adds shared pie-chart SVG utilities and reuses them in both Bubble and 2D Network rendering.
• Preserves color opacity/transparency in collapsed pie rendering.
• Improves SVG export so collapsed pie images remain embedded and get proper outlines.
• Refreshes collapse controls when global distance metric or display format changes.
• Fixes 2D render/update handling for aggregate node IDs and retargeted Cytoscape edges.
• Adds minor 2D UI layering and button styling corrections.
• Adds Cypress coverage for collapse behavior, warnings, tooltips, SVG export, and metric/format control updates.
• Adds collapse-specific Cypress fixtures for mean-distance validation.