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/41-future-tense.md

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+# 41. Future Tense
+
+> Source: [A Complete Guide To Every Fundamental In Spanish (The Conclusion)](https://youtube.com/watch?v=YHDZSHCt1DE&t=11381s)
+
+The simple future tense expresses what *will* happen. Spanish keeps the full infinitive and adds one of six endings — the same set for `-ar`, `-er`, and `-ir` verbs.
+
+## Key Rules
+- Take the **infinitive** (do not drop the ending) and add: `-é, -ás, -á, -emos, -éis, -án`.
+- All endings carry an accent **except** the `nosotros` form (`-emos`).
+- Stem-changes don't affect the future of regular verbs.
+- A small set of verbs use **irregular stems** with the same endings: `decir → dir-`, `hacer → har-`, `poder → podr-`, `poner → pondr-`, `querer → querr-`, `saber → sabr-`, `salir → saldr-`, `tener → tendr-`, `venir → vendr-`, `haber → habr-`.
+- Object pronouns and `no` go before the conjugated future form: `Yo te lo daré`.
+- Alternative: `ir a` + infinitive (`Voy a comer`) expresses the near future and is more common in conversation.
+
+## Conjugation / Pattern Tables
+
+### Regular endings (added to infinitive)
+| Pronoun | Ending |
+|---|---|
+| yo | -é |
+| tú | -ás |
+| él | -á |
+| nosotros | -emos |
+| vosotros | -éis |
+| ellos | -án |
+
+### Sample regular: `hablar`
+| yo | hablaré |
+| tú | hablarás |
+| él | hablará |
+| nosotros | hablaremos |
+| vosotros | hablaréis |
+| ellos | hablarán |
+
+### Common irregular stems
+| Infinitive | Stem | yo form |
+|---|---|---|
+| decir | dir- | diré |
+| hacer | har- | haré |
+| poder | podr- | podré |
+| poner | pondr- | pondré |
+| querer | querr- | querré |
+| saber | sabr- | sabré |
+| salir | saldr- | saldré |
+| tener | tendr- | tendré |
+| venir | vendr- | vendré |
+| haber | habr- | habré |
+
+## Examples
+| Spanish | English |
+|---|---|
+| Yo haré mi tarea. | I will do my homework. |
+| Tú comprarás una casa en el futuro. | You will buy a house in the future. |
+| Él tendrá 30 años. | He will be 30 years old. |
+| Nosotros aprenderemos español mañana. | We will learn Spanish tomorrow. |
+| Ellos vendrán si quieren. | They will come if they want. |
+| Yo te lo daré. | I will give it to you. |
+| Él se bañará. | He will take a bath. |
+| ¿Qué harás mañana? | What will you do tomorrow? |
+| Nosotros saldremos pronto. | We will leave soon. |
+| Yo iré a la escuela. | I will go to the school. |
+| Yo voy a ir a la escuela. | I am going to go to the school. |
+
+## Notes & Gotchas
+- Use `tener` for ages: `tendrá 30 años` (not `será`).
+- `Ir a + infinitive` (`voy a + verb`) is the easier "future" replacement and very common.
+- The simple future can also express probability/conjecture in the present: `¿Dónde estará?` (Where could he be?).
+- Don't drop the accent on `-é, -ás, -á, -éis, -án` — it's required.