Explore an Extras tab for optional companion content, AI features, and playful additions

## Direction

Add an **Extras** tab for optional practical, personal, AI-generated, and playful companion content. This issue collects the complete brainstorming list; the ideas are candidates, not a commitment to implement every feature in the first release.

**Enabled extras must appear in Contents**, where users can include/exclude them and arrange them alongside original book sections using drag and drop or a numeric position. Contents should be the shared place to control final printed order, not a second competing ordering interface in Extras.

Related: #59 — Contents reordering.

## Shared behavior

- All extras are optional. Ordinary book rendering stays unchanged until an extra is enabled.
- Give extras stable IDs, titles, editable content, and sensible length controls. Offer spoiler controls where relevant and clearly label generated companion material.
- Enabling an extra adds it to Contents at a predictable initial position; users can then move it there. Disabling it should preserve its content for reuse.
- Generate AI content explicitly and separately from **Apply**. Save the result and reuse it when print settings change; ordinary Apply must not regenerate AI content or trigger repeated AI charges.
- Allow review and editing before generated material is included in the PDF.
- Show the actual effect on printed-side/sheet counts after successful layout; do not invent page counts for an unapplied draft.
- Preserve draft/Apply/Revert, failed-render recovery, per-document isolation, and immutable kept versions. Record the actual extra content used by a completed layout, not merely the prompt that generated it.
- Preserve source attribution for online material. Reviews must come from real sources; do not present invented AI reviews as fetched reviews. Spoiler-sensitive content needs appropriate controls.
- Keep non-AI extras usable without an AI service. Decide provider, credentials, privacy, and cost behavior before enabling AI generation, especially for the zero-cost Cloudflare edition. Never introduce an automatic paid fallback.
- Explain what text is sent to an AI or external service before generation. Respect the hosted edition's temporary-book lifetime for saved extras too.

## Useful reading companions

1. **Previously in this book:** recap up to a selected chapter, excluding later events.
2. **Character cheat sheet:** names, aliases, relationships, and brief reminders.
3. **Relationship diagram:** a compact visual of who is connected to whom.
4. **Glossary:** unfamiliar vocabulary, invented terms, technical jargon, and historical references.
5. **Timeline:** chronological events, particularly for nonlinear narratives.
6. **One-page companion:** key people, places, and concepts on one reference sheet.
7. **Chapter summaries:** a sentence or paragraph per chapter, optionally gathered at the back.
8. **Technical study sheet:** definitions, formulas, and worked examples for nonfiction.
9. **Further reading:** related books and background sources with printable URLs.
10. **Discussion questions:** prompts for a book club, classroom, or personal reflection.

## Personal extras that do not require AI

11. **Notes pages:** blank, ruled, dotted, or annotation space.
12. **Reading journal:** start/finish dates, favorite passages, thoughts, and a personal rating.
13. **Your own foreword or dedication:** why you chose the book or a message to its recipient.
14. **Custom content:** add text, Markdown, images, an essay, or a review.
15. **Reading checklist:** chapters with boxes to mark as completed.
16. **Quote collection:** user-selected passages with printed locations.
17. **Printable bookmark:** title, chapter checklist, or a compact character reference.
18. **Edition card:** printed-by name, date, chosen layout details, and optional edition number.
19. **Lending card:** borrower, lending date, and return date in an old-library style.

## AI and sourced companions

20. **Before-you-read briefing:** setting, historical background, and useful context without plot spoilers.
21. **Fact versus fiction:** sourced context for real people/events and the novel's inventions.
22. **Argument map:** a nonfiction book's claims, evidence, assumptions, and counterarguments.
23. **Two opposing interpretations:** plausible alternative readings of a character, theme, or ending.
24. **Questions worth sitting with:** deeper reflection prompts about choices, motives, and themes.
25. **Explain the difficult bit:** a plain-language explanation of a selected passage.
26. **A skeptical reader's notes:** claims to investigate, unclear reasoning, and competing explanations.
27. **Review sampler:** attributed perspectives from real online reviews, with links and spoiler controls.
28. **What reviewers disagree about:** differences over pacing, characters, endings, accuracy, and other themes, rather than just an average rating.

## Playful and experimental extras

29. **The plot as meeting minutes:** action items and unresolved agenda items.
30. **Character performance reviews:** strengths, development areas, and disastrous judgment calls.
31. **The book as a bug report:** steps to reproduce the disaster; expected versus actual behavior.
32. **An unofficial survival field guide:** how to survive the book's world or its fictional organization.
33. **A fictional newspaper front page:** events reported from inside the story.
34. **Alternate back-cover blurbs:** brutally honest, melodramatic, bureaucratic, or deadpan.
35. **A character's terrible advice column.**
36. **A mock legal complaint:** the protagonist versus everyone who complicated their life.
37. **A plot decision tree:** where one sensible conversation might have prevented the disaster.
38. **A tiny crossword or word search:** characters, places, and concepts.
39. **Reading bingo:** ominous weather, avoidable misunderstandings, withheld explanations, and other patterns.
40. **Absurdly specific awards:** best supporting bad decision, most suspicious coincidence, and similar categories.
41. **A six-panel recap comic:** a later visual-generation experiment.
42. **A deliberately bad summary:** clearly labeled comedy, recognizable but intentionally ridiculous.

## Suggested first slice, subject to design

Start with custom content and notes pages to establish the Extras-to-Contents integration without an AI dependency. Then consider a character/glossary companion, optional summaries, and a few playful templates. Build shared editing, persistence, ordering, and print behavior before expanding the catalog.

No files or tests are named in the issue. Start by reading related issue #59 and scope the suggested first slice: custom content and notes pages. Done means extras can be edited and persisted, enabled items appear in Contents for ordering, and printed output reflects them without requiring AI.

Written by the indexing model from the issue text.