Integrate Native Neovim Multicursor

Integration Proposal

The main constraint is that Neovim cannot take over input handling in Insert mode, as this would interfere with VS Code features such as completion and other input-related behavior. Therefore, 100% compatibility with Neovim multicursor is not possible.

Instead, we can bridge Neovim multicursor and VS Code multi-selection based on the current editor mode:

• Non-Insert mode: use Neovim's native multicursor directly.
• Entering Insert mode: convert the Neovim multicursor state into VS Code multi-selection, allowing VS Code to handle text input and completion.
• Leaving Insert mode: synchronize the VS Code multi-selection back to Neovim's multicursor state.
• During mode changes: keep both states synchronized so the transition is seamless.

This gives us the benefits of Neovim's native multicursor commands while preserving VS Code's native input and completion functionality.