docs: Update launch docs with unified messaging, add visual asset specs

- Update LAUNCH_SUMMARY.md to use 5 Problems / 6 Solutions framework
- Remove old 87% confidence claims and narrow hospital→deployment focus
- Rewrite marketing README.md with new content index
- Add VISUAL_ASSET_SPECS.md with detailed specs for stock/AI image creation

Visual asset specs include:
- Product Hunt thumbnail (1270x760)
- Memory architecture diagram
- 5 Problems / 6 Solutions infographic
- Quick start terminal screenshot
- Social media cards
- AI image generation prompts
- Color palette and typography

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: silversurfer562