Added system prompt for Google's new Antigravity AI coding assistant, announced November 18, 2025. Antigravity is an agent-first coding tool with support for Gemini 3 Pro and third-party models. Source: p1njc70r (https://x.com/p1njc70r/status/1990919996265148701) - Added SystemPrompts/Google/11182025-Antigravity.md - Updated SystemPrompts/README.md index