Antigravity 1.1.9: Slash-command expansion in print mode, non-blocking MCP startup, session-wide permission memory, system temp directory write grants, and hook and UI stability fixes

Added slash-command and skill expansion in print mode, non-blocking background MCP loading during interactive startup, session-scoped permission pattern recording, system temporary directory write grants, and stability fixes for stop/PostToolUse hooks, artifact viewer, and MCP authentication.