Add 13 new grammar notes with 1010 exercises from video extraction

Scraped a 4h Spanish fundamentals YouTube video (transcript + OCR on
14810 frames), extracted structured content across 52 chapters, and
generated fill-in-the-blank quizzes for every grammar topic.

- 13 new GrammarNote entries (articles, possessives, demonstratives,
  greetings, poder, al/del, prepositional pronouns, irregular yo,
  stem-changing, stressed possessives, present/future perfect, present
  indicative conjugation)
- 1010 generated exercises across all 36 grammar notes (new + existing)
- Fix tense guide parser to handle unnumbered *Usages* blocks
- Rewrite 6 broken tense guide bodies (imperative, subj pluperfect,
  subj future) with numbered usage format
- Bump courseDataVersion 5→6 with TenseGuide refresh on upgrade
- Add docs/spanish-fundamentals/ with raw transcripts, polished notes,
  structured JSON, and exercise data

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/spanish-fundamentals/notes/52-the-conclusion.md

@@ -0,0 +1,17 @@
+# 52. The Conclusion
+
+> Source: [A Complete Guide To Every Fundamental In Spanish](https://youtube.com/watch?v=YHDZSHCt1DE&t=14730s)
+
+A short closing message wrapping up the full Spanish fundamentals series. The narrator clarifies the goal of the series and acknowledges the polyglot-paced delivery.
+
+## Key Points
+
+- The goal of the series wasn't to teach you to *speak* Spanish, but to teach you how to *think* in Spanish — the system underneath the language.
+- Everyone learns differently, but everyone has to know and understand the **fundamentals** of any language before mastering it.
+- The compact, fast format was an intentional choice to avoid wasting time; the narrator apologizes if it felt rushed.
+- Once you internalize the fundamentals, you can pick whatever speaking method fits you to actually master the language.
+
+## Notes & Gotchas
+
+- No new grammar in this chapter — pure outro.
+- If a concept felt too fast on first pass, the recommendation is implicit: rewatch the specific chapter rather than the whole video.