FEAT: Split View, Keyboard Shortcuts, and SQL Editor Font Size Control

[falconluca]

1. Add a split view to allow the SQL Editor and AI Shell to be visible and usable at the same time.
2. Improve productivity by supporting more keyboard shortcuts (e.g. duplicate line, toggle dropdowns via keyboard).
3. Allow users to adjust the font size inside the SQL editor, preferably via shortcuts and/or editor settings.