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/gustar-like-verbs.json

@@ -0,0 +1,66 @@
+[
+  {
+    "sentence": "A mí me _____ la pizza.",
+    "correct": "gusta",
+    "distractor": "gustan",
+    "explanation": "Pizza is singular, so use gusta.",
+    "source_chapter": "20",
+    "source_title": "The Verb Gustar"
+  },
+  {
+    "sentence": "A nosotros nos _____ los tacos.",
+    "correct": "gustan",
+    "distractor": "gusta",
+    "explanation": "Tacos is plural, so use gustan.",
+    "source_chapter": "20",
+    "source_title": "The Verb Gustar"
+  },
+  {
+    "sentence": "A ellos _____ gusta jugar fútbol.",
+    "correct": "les",
+    "distractor": "le",
+    "explanation": "Plural ellos requires plural IOP les.",
+    "source_chapter": "20",
+    "source_title": "The Verb Gustar"
+  },
+  {
+    "sentence": "Me _____ bailar y cantar.",
+    "correct": "gusta",
+    "distractor": "gustan",
+    "explanation": "Multiple infinitives still take singular gusta.",
+    "source_chapter": "20",
+    "source_title": "The Verb Gustar"
+  },
+  {
+    "sentence": "A Juan _____ gusta el café.",
+    "correct": "le",
+    "distractor": "lo",
+    "explanation": "Gustar requires an IOP (le), not a DOP.",
+    "source_chapter": "20",
+    "source_title": "The Verb Gustar"
+  },
+  {
+    "sentence": "_____ ti te gustan las películas.",
+    "correct": "A",
+    "distractor": "Para",
+    "explanation": "Clarification structure uses a, not para.",
+    "source_chapter": "20",
+    "source_title": "The Verb Gustar"
+  },
+  {
+    "sentence": "A María le _____ los gatos.",
+    "correct": "gustan",
+    "distractor": "gusta",
+    "explanation": "Gatos is plural; verb agrees with the subject.",
+    "source_chapter": "20",
+    "source_title": "The Verb Gustar"
+  },
+  {
+    "sentence": "Me _____ hablar contigo.",
+    "correct": "gusta",
+    "distractor": "gustan",
+    "explanation": "Hablar is a singular infinitive.",
+    "source_chapter": "20",
+    "source_title": "The Verb Gustar"
+  }
+]