TopoViewer Grid: unified manager, UI line width control, and persistent viewer settings

[asadarafat]

Summary

• Centralizes grid drawing and snapping config in a single ManagerGridGuide.
• Adds a “Grid line width” slider in the layout drawer to adjust the overlay in real time.
• Persists the chosen line width in annotations under viewerSettings.gridLineWidth.
• Removes legacy grid configuration code to reduce duplication and drift.

What’s Included

• Refactor: Introduce ManagerGridGuide to own overlay rendering and cytoscape-grid-guide options;
  dedupe theme colors and align default spacing.
• Feature: UI control to adjust grid line width (0.10–2.00, step 0.05; default 0.5 [as previous]); updates both
  overlay and plugin visuals immediately.
• Chore: Remove obsolete gridGuide.ts to avoid conflicting sources of truth.
• Feature: Persist grid line width via annotations
  • Adds TopologyAnnotations.viewerSettings.gridLineWidth.
  • New extension endpoints: topo-editor-load-viewer-settings, topo-editor-save-viewer-settings.
  • Preserve viewerSettings on other annotation saves to avoid accidental loss.

Motivation

• Make grid behavior and visuals consistent, easier to maintain, and quick to tweak from the UI.
• Ensure user preferences survive reloads and are stored alongside other viewer-related
  annotations.

Developer Notes

• ManagerGridGuide clamps line width to 0.1–2.0 and requests redraw with each change.
• Theme detection is centralized; plugin options re-applied when spacing/line width/theme changes.
• The legacy grid utilities were removed; all grid responsibilities live in ManagerGridGuide now.

Testing Instructions

CleanShot.2025-10-26.at.22.13.52.mp4

• Open TopoViewer in edit mode.
• Layout drawer -> adjust “Grid line width”; verify overlay thickness updates live.
• Reload the webview; verify the line width restores from annotations.
• Toggle VS Code theme; confirm grid color adapts and line width persists.
• Validate grid snapping still works as before (drag and release nodes onto the grid).

Compatibility / Migration

• Annotations files without viewerSettings will default to 0.5 line width; saving will add
  viewerSettings as needed.
• Requires the extension-side endpoints shipped in this PR; older extension builds won’t persist
  the setting.

Housekeeping

• No runtime behavior change to YAML persistence, only annotations.