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/exercises/seed/present-indicative-conjugation.json

@@ -0,0 +1,50 @@
+[
+  {
+    "sentence": "Yo _____ español todos los días.",
+    "correct": "hablo",
+    "distractor": "hablas",
+    "explanation": "yo takes -o in -ar verbs: hablo.",
+    "source_chapter": "03",
+    "source_title": "Conjugating Verbs (Present)"
+  },
+  {
+    "sentence": "Tú _____ pizza los viernes.",
+    "correct": "comes",
+    "distractor": "comen",
+    "explanation": "tú takes -es in -er verbs: comes.",
+    "source_chapter": "03",
+    "source_title": "Conjugating Verbs (Present)"
+  },
+  {
+    "sentence": "Nosotros _____ en Madrid.",
+    "correct": "vivimos",
+    "distractor": "vivís",
+    "explanation": "nosotros + -ir = -imos.",
+    "source_chapter": "03",
+    "source_title": "Conjugating Verbs (Present)"
+  },
+  {
+    "sentence": "Ellos _____ con sus amigos.",
+    "correct": "hablan",
+    "distractor": "habla",
+    "explanation": "ellos + -ar = -an.",
+    "source_chapter": "03",
+    "source_title": "Conjugating Verbs (Present)"
+  },
+  {
+    "sentence": "Ella _____ mucho café.",
+    "correct": "come",
+    "distractor": "como",
+    "explanation": "ella + -er = -e (like the él form).",
+    "source_chapter": "03",
+    "source_title": "Conjugating Verbs (Present)"
+  },
+  {
+    "sentence": "Yo _____ cerca de la escuela.",
+    "correct": "vivo",
+    "distractor": "vive",
+    "explanation": "yo + -ir = -o.",
+    "source_chapter": "03",
+    "source_title": "Conjugating Verbs (Present)"
+  }
+]