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-perfect-tense.json

@@ -0,0 +1,66 @@
+[
+  {
+    "sentence": "Yo _____ hablado con él. (haber)",
+    "correct": "he",
+    "distractor": "ha",
+    "explanation": "yo + haber = he.",
+    "source_chapter": "39",
+    "source_title": "Present Perfect Tense"
+  },
+  {
+    "sentence": "Tú _____ comido demasiado. (haber)",
+    "correct": "has",
+    "distractor": "ha",
+    "explanation": "tú + haber = has.",
+    "source_chapter": "39",
+    "source_title": "Present Perfect Tense"
+  },
+  {
+    "sentence": "Nosotros _____ vivido aquí cinco años.",
+    "correct": "hemos",
+    "distractor": "habemos",
+    "explanation": "nosotros + haber = hemos.",
+    "source_chapter": "39",
+    "source_title": "Present Perfect Tense"
+  },
+  {
+    "sentence": "Ella ha _____ una carta. (escribir)",
+    "correct": "escrito",
+    "distractor": "escribido",
+    "explanation": "Escribir is irregular: escrito.",
+    "source_chapter": "39",
+    "source_title": "Present Perfect Tense"
+  },
+  {
+    "sentence": "¿_____ visto la película? (tú, haber)",
+    "correct": "Has",
+    "distractor": "Hes",
+    "explanation": "tú form is 'has'.",
+    "source_chapter": "39",
+    "source_title": "Present Perfect Tense"
+  },
+  {
+    "sentence": "John no me _____ ha dicho.",
+    "correct": "lo",
+    "distractor": "le",
+    "explanation": "DOP 'lo' goes before haber along with IOP me.",
+    "source_chapter": "39",
+    "source_title": "Present Perfect Tense"
+  },
+  {
+    "sentence": "Yo _____ tenido muchos amigos.",
+    "correct": "he",
+    "distractor": "tengo",
+    "explanation": "Use haber + tenido for 'have had'.",
+    "source_chapter": "39",
+    "source_title": "Present Perfect Tense"
+  },
+  {
+    "sentence": "I have to read = Yo _____ que leer.",
+    "correct": "tengo",
+    "distractor": "he",
+    "explanation": "Obligation uses tener que, not haber.",
+    "source_chapter": "39",
+    "source_title": "Present Perfect Tense"
+  }
+]