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/03-conjugating-verbs-present.md

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+# 03. Conjugating Verbs (Present)
+
+> Source: [video link](https://youtube.com/watch?v=YHDZSHCt1DE&t=632s)
+
+The "primary fundamental" of Spanish: how regular verbs end in **-ar / -er / -ir**, and the six person-conjugations you produce by dropping the infinitive ending and adding a person-specific ending. Walks through *hablar*, *comer*, and *vivir* as the canonical models.
+
+## Key Rules
+- A Spanish infinitive must end in **-ar**, **-er**, or **-ir** (English infinitives are marked by the preposition "to": to eat, to walk).
+- Conjugation = drop the infinitive ending → add the person ending matching the subject pronoun.
+- Spanish has **6** person endings per tense (vs. English's 2 in the present).
+- *-er* and *-ir* share four of six endings (yo, tú, él, ellos), making the systems similar.
+- Focus first on **yo / tú / él / ellos** — these dominate everyday speech. *Nosotros* and *vosotros* matter but are less frequent.
+
+## Present-tense Endings
+
+| Pronoun | -ar | -er | -ir |
+|---------|-----|-----|-----|
+| yo | -o | -o | -o |
+| tú | -as | -es | -es |
+| él / ella / usted | -a | -e | -e |
+| nosotros/as | -amos | -emos | -imos |
+| vosotros/as | -áis | -éis | -ís |
+| ellos/as / ustedes | -an | -en | -en |
+
+## Conjugation: hablar (to speak)
+
+| Pronoun | Form |
+|---------|------|
+| yo | hablo |
+| tú | hablas |
+| él / ella / usted | habla |
+| nosotros/as | hablamos |
+| vosotros/as | habláis |
+| ellos/as / ustedes | hablan |
+
+## Conjugation: comer (to eat)
+
+| Pronoun | Form |
+|---------|------|
+| yo | como |
+| tú | comes |
+| él / ella / usted | come |
+| nosotros/as | comemos |
+| vosotros/as | coméis |
+| ellos/as / ustedes | comen |
+
+## Conjugation: vivir (to live)
+
+| Pronoun | Form |
+|---------|------|
+| yo | vivo |
+| tú | vives |
+| él / ella / usted | vive |
+| nosotros/as | vivimos |
+| vosotros/as | vivís |
+| ellos/as / ustedes | viven |
+
+## Examples
+
+| Spanish | English |
+|---------|---------|
+| Yo hablo español. | I speak Spanish. |
+| Yo hablo ruso. | I speak Russian. |
+| Yo hablo contigo. | I'm speaking with you. |
+| Como pizza. | I eat pizza. |
+| Vivimos en Madrid. | We live in Madrid. |
+
+## Notes & Gotchas
+- *Como* (I eat) is also the word for "like / as" (e.g., *como te dije ayer* — "as I told you yesterday"). Context disambiguates.
+- The pattern only covers **regular** verbs. Many useful verbs (*ser, estar, ir, tener, pensar, gustar*) are irregular or stem-changing and are covered in their own chapters.
+- Subject pronouns are often dropped because the verb ending already encodes the person.