Antigravity 1.1.13: GEMINI_API_KEY authentication, custom agent task management, embedded ripgrep caching, and conversation database fixes

Direct GEMINI_API_KEY authentication support, /codesearch fallback resilience, cached artifact list scrolling, manage_task access for custom declarative agents, embedded ripgrep caching with SHA-256 verification, and critical fixes for trajectory truncation, database growth, transcript race conditions, and subagent path validation.