docs: Simplify roadmap-priorities.md - reduce verbosity by 77%

- Reduced from 562 lines to 128 lines
- Removed redundant tables, excessive metadata, and filler text
- Converted verbose descriptions to bullet points
- Kept essential information: packages, priorities, success criteria
- Focus on WHAT and WHY, not excessive HOW details
- Removed obvious statements and repeated information

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

Author: abrichr