📐 [Core] Add Document Snapping Support

[ahmdkaml]

📐 Overview

Add snapping support to TextForge's document layout system.

Snapping should allow compatible document elements to align automatically with relevant layout boundaries or other elements.

🎯 Goals

• Define a Core snapping model.
• Allow supported elements to snap to defined alignment targets.
• Keep snapping deterministic.
• Ensure snapping does not interfere with normal document layout.
• Make the system extensible for future layout interactions.

🌱 Future Direction

The snapping system may eventually support relationships such as:

• Module-to-module alignment
• Page margins
• Grid lines
• Columns
• Guides
• Containers

The exact snapping targets and interaction behavior should be defined before implementation.