fix: pre-calculate cluster node positions and reduce drag disturbance

[Shanb007]

Summary

Fixes #3

Cluster topology graph nodes rendered tightly clustered on initial load and slowly animated apart. Additionally, clicking/dragging any single node caused all other nodes to reposition.

Changes

Pre-calculate initial node positions based on role

• Master nodes are placed in a circle around the center of the canvas
• Replica nodes are placed offset outward from their respective master
• Saved positions (from previous drag) are still respected
• This eliminates the tight clump -> slow spread animation on first render

Increase alphaDecay (0.0228 -> 0.05)

• The simulation now settles ~2x faster since nodes already start in good positions
• Only minor adjustments needed, no reason for a long animation

Lower drag alphaTarget (0.3 -> 0.01)

• Previously, clicking any node reheated the entire force simulation to 0.3, causing all nodes to reposition
• Now it only warms enough for links to follow the dragged node without disturbing neighbors

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Note

Low Risk
UI-only layout/interaction changes confined to a single visualization component; main risk is unintended node placement or responsiveness issues on resize.

Overview
Improves the initial layout and interaction stability of the ClusterTopologyGraph by precomputing deterministic node positions (masters in a circle, replicas offset from their master) while still honoring any drag-saved positions.

Tweaks the D3 force simulation to settle faster and avoid disturbing the whole graph on drag: alphaDecay is increased and drag start uses a much lower alphaTarget; simulation “needs run” detection now keys off presence in nodePositionsRef rather than missing x/y (and layout now recalculates when containerWidth changes).

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