docs(studio): streamline roadmap with realistic 3-phase plan for 2026

Agent-Logs-Url: https://github.com/objectstack-ai/framework/sessions/aee98dea-df58-4f92-a469-2ee65abf4a2d

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Claude