Allow basic viewer settings NG manipulation, tool use, defaults in the front end.

[mattjdavis]

1. Add top-level settings
   Update the state dict to include the following viewer settings.
   Each time a new Neuroglancer link is provided, check for these keys and add them if missing.

   "showScaleBar": True,
   "showDefaultAnnotations": False,
   "layout": "xy",  # options: "xy", "xz", "yz", "3d", "4panel"
   "showAxisLines": False

2. Expose settings to tools
   Make sure all tools can read and update these settings in the state dict.

3. Frontend updates

   • Add a Viewer card to the settings sidebar.
   • When a new Neuroglancer link is loaded, apply the default viewer settings listed above.
   • Ensure users can modify these settings through the UI.

[mattjdavis]

Viewer-Level Settings Feature

Summary

Added viewer display settings (scale bar, axis lines, annotations, layout) with LLM control, UI widgets, and user-configurable defaults applied when loading new Neuroglancer links.

Implementation

Backend

• New tool: ng_set_viewer_settings - LLM can modify viewer settings via natural language
• Model: NgSetViewerSettings with optional fields: showScaleBar, showDefaultAnnotations, showAxisLines, layout
• State management: Added set_viewer_settings() method to NeuroglancerState class
• Smart defaults: StateLoad endpoint accepts default_settings from frontend, applies only if missing from URL, returns updated_url when applied

Frontend

• UI: New "Viewer Settings" card in right sidebar with 4 controls (3 checkboxes + 1 dropdown)
• Bidirectional sync: Widget changes update backend immediately; widgets sync from backend after state loads
• Defaults flow: Widget values passed to backend on each load → applied if missing → viewer reloaded with updated URL if needed

Key Features

• Settings panel acts as both current state display and default preferences
• Explicit URL settings always override user defaults
• No hardcoded defaults - fully user-controlled
• Settings persist in saved/shared URLs
• Backward compatible with existing URLs

Files Modified

• models.py, neuroglancer_state.py, constants.py, main.py, llm.py, panel_app.py