docs: simplify roadmap and fix Python version claims

Consolidates PRs #981 and #982:
- Reduce roadmap from 562 to ~125 lines (77% reduction)
- Remove verbose tables and redundant sections
- Update openadapt-ml to show >=3.10 (PR #5 fixes this)
- Remove Python version mismatch from technical debt
- Correct accuracy claim to 46.7% -> 100%

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: abrichr