MapControls: Improve panning accuracy

[mrdoob]

Description

This PR improves the panning logic in MapControls to ensure the point under the mouse cursor remains exactly under the cursor during panning ("sticky" panning). Previously, the panning used an approximation that could cause drift, especially when panning far from the center.

Before	After
Screen.Recording.2025-11-21.at.5.08.07.PM.mov	Screen.Recording.2025-11-21.at.5.08.24.PM.mov

Changes

• Implemented raycasting-based panning to calculate precise world-space deltas.

Test

• Verified that the point under the cursor stays fixed relative to the cursor while dragging.
• Verified that damping works as expected (smooth catch-up).
• Verified that enabling screenSpacePanning restores the original screen-space panning behavior.

(Made using https://antigravity.google/ with Gemini 3.0)