Stabilize code graph interactions

[forhappy]

Summary

• stop vis-network physics synchronously before a stabilized graph becomes interactive
• automatically pause a running layout when the user hovers a node or starts dragging
• keep the shared HTML export and VS Code graph behavior aligned
• regenerate the embedded viewer bundle and add stationary-frame browser coverage

Root cause

The viewer published stabilizationIterationsDone to React before directly stopping vis-network. vis-network can continue its dynamic phase after that event, so the loading layer could disappear while nodes were still drifting. Explicitly resumed layouts also kept moving while the pointer approached a node, making click targets difficult to acquire.

User impact

Code nodes remain stationary once rendered. If a user explicitly runs the automatic layout, beginning a node interaction locks the current positions immediately, preserving reliable hover, focus, click, drag, and source navigation in both self-contained HTML exports and the VS Code extension.

Validation

• npm run typecheck:js
• npm run test:js
  • 196 shared viewer tests
  • 120 VS Code tests
  • 83 Chromium UX, accessibility, and performance tests
• node scripts/check_viewer_assets.mjs
• git diff --check