docs: fix stars rendering and add new feature documentation

Fix critical markdown rendering issue where "software **adapt**er" displayed
with literal stars instead of bold formatting. Update package documentation
with comprehensive coverage of new features: episode segmentation, recording
catalog, advanced search, and screenshot automation.

Changes:
- Fix: Remove nested bold formatting causing stars to render literally
- Add: Screenshot autogeneration script (450 lines, Playwright-based)
- Add: Episode segmentation documentation (ML package)
- Add: Recording catalog system documentation (viewer package)
- Add: Advanced search documentation (viewer package)
- Add: Component library reference (viewer package)
- Add: Comprehensive change summary (DOCS_UPDATE_SUMMARY.md)
- Update: Viewer documentation (+148% expansion, 136→336 lines)
- Update: ML documentation (+79% expansion, 155→277 lines)

Files modified:
- docs/index.md (fix stars issue)
- docs/design/landing-page-strategy.md (fix stars issue)
- docs/packages/viewer.md (add new features)
- docs/packages/ml.md (add episode segmentation)

Files created:
- docs/_scripts/generate_docs_screenshots.py (screenshot automation)
- docs/_scripts/README.md (script documentation)
- docs/DOCS_UPDATE_SUMMARY.md (comprehensive summary)

This addresses user-reported issues with documentation quality and ensures
all January 2026 features are properly documented with examples, schemas,
and usage patterns.

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

Author: abrichr