docs: overhaul ROADMAP.md - simplify completed work, refocus on component excellence and developer experience

Reduces ROADMAP from 700 to 296 lines (58% reduction):
- Condense all completed Q1-Q3 milestones into brief paragraph summaries
- Remove individual checkbox noise for completed items
- Set new short-term priority: Component Excellence, Console Completeness, Developer Experience, Documentation
- Defer marketplace, plugin marketplace, cloud, and commercialization to Future Vision section
- Add concrete success metrics table
- Simplify risk management and resource sections

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

Author: Copilot