[FEATURE] Setting to open the /diff panel on the left instead of the right

Feature request

Add a setting to choose which side of the screen the /diff panel (file changes view) opens on in the CLI, so it can be docked on the left instead of the right.

Why

The diff panel always opens on the right. For people whose editor/terminal layout keeps code on the left, a right-side diff means constantly looking back and forth across the screen. A left/right option would let the panel sit where the eye already is.

Suggested shape

• A settings.json key (e.g. "diffPanelPosition": "left" | "right", default right), also exposed in /config
• Optionally a keybinding to swap sides on the fly

Environment

• Claude Code CLI, macOS