New Grid Picker, AI Assistant Improvements, and UI Polish

New Features

• Visual card-based grid picker replaces the old dropdown selection
• Demo grids accessible directly from the picker

Improvements

• Tessa AI: better error handling and faster responses
• Pixel-perfect UI layout and font sizing
• Clearer connection failure dialogs
• Improved grid card selection visibility

Bug Fixes

• Fixed time-range tool queries
• Fixed input action handling on world canvases
• General stability fixes