Clean up al-folio template cruft for personal one-page site

Remove leftover theme demo content, documentation, and unused pages so
the repo only contains what this personal site actually uses.

Demo content:
- _pages/about_einstein.md, _pages/profiles.md (demo "people" page)
- _books/the_godfather.md + book_covers, unused prof_pic_1/template_error images

Unused pages & layouts (one-page layout kept; nav = Publications/Projects/Teaching):
- _pages/books.md, _pages/dropdown.md
- _layouts/book-review.liquid, _layouts/book-shelf.liquid
- Drop the `books` collection and its archives from _config.yml

Theme documentation (not needed for a personal site):
- README, CUSTOMIZE, FAQ, INSTALL, QUICKSTART, SEO, TROUBLESHOOTING,
  ANALYTICS, CONTRIBUTING, .all-contributorsrc, readme_preview/, lighthouse_results/

Housekeeping:
- AGENTS.md: drop links to the removed docs
- _config.yml: drop stale `exclude` entries for deleted files

Verified: Docker build succeeds and the site serves correctly at localhost:8080.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: JWRoboticsVision

.all-contributorsrc

@@ -7,10 +7,6 @@ A simple, clean, and responsive Jekyll theme for academics.
 - **Are you a coding agent?** → Read [`.github/copilot-instructions.md`](.github/copilot-instructions.md) first (tech stack, build, CI/CD, common pitfalls & solutions)
 - **Customizing the site?** → See [`.github/agents/customize.agent.md`](.github/agents/customize.agent.md)
 - **Writing documentation?** → See [`.github/agents/docs.agent.md`](.github/agents/docs.agent.md)
-- **Need setup/deployment help?** → [INSTALL.md](INSTALL.md)
-- **Troubleshooting & FAQ?** → [TROUBLESHOOTING.md](TROUBLESHOOTING.md)
-- **Customization & theming?** → [CUSTOMIZE.md](CUSTOMIZE.md)
-- **Quick 5-min start?** → [QUICKSTART.md](QUICKSTART.md)
 
 ## Essential Commands
 
@@ -77,5 +73,4 @@ When modifying `_config.yml`, these **must be updated together**:
 For troubleshooting, see:
 
 - [Common Pitfalls & Workarounds](.github/copilot-instructions.md#common-pitfalls--workarounds) in copilot-instructions.md
-- [TROUBLESHOOTING.md](TROUBLESHOOTING.md) for detailed solutions
 - [GitHub Issues](https://github.com/alshedivat/al-folio/issues) to search for your specific problem.