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/05-the-verb-ser.md

@@ -0,0 +1,52 @@
+# 05. The Verb "Ser"
+
+> Source: [video link](https://youtube.com/watch?v=YHDZSHCt1DE&t=1134s)
+
+*Ser* means "to be / to exist" and is one of two Spanish verbs for "to be" (the other is *estar*). *Ser* is highly irregular and is reserved for **factual** statements about a subject — name, nationality, occupation, physical traits, generalizations, where/when an event happens, and time/date.
+
+## Key Rules
+- *Ser* is irregular — there's no derivable pattern, so memorize the six forms.
+- Use *ser* for things that are factually, identity-defining true about a subject:
+  1. **Name, nationality, place of origin** — *Yo soy Alex. / Soy español. / Soy de España.*
+  2. **Occupation** — *Él es profesor.* (no indefinite article before the profession)
+  3. **Physical traits** (about oneself, considered factual) — *Tú eres bonito/a.*
+  4. **Generalizations** — *Es importante trabajar.*
+  5. **Where / when an event takes place** — *La fiesta es en el club. / La fiesta es a las seis.*
+  6. **Time and date** — *Es lunes. / Es la una de la tarde. / Son las dos de la tarde.*
+- Don't put an indefinite article before a profession after *ser*: *Él es profesor*, NOT *Él es un profesor*.
+- Time uses *es* for one o'clock (singular) and *son* for two o'clock and beyond (plural): *Es la una. / Son las dos.*
+- Always include the article *la / las* with clock time: *Es la una, son las tres*.
+
+## Conjugation: ser (present indicative)
+
+| Pronoun | Form |
+|---------|------|
+| yo | soy |
+| tú | eres |
+| él / ella / usted | es |
+| nosotros/as | somos |
+| vosotros/as | sois |
+| ellos/as / ustedes | son |
+
+## Examples
+
+| Spanish | English |
+|---------|---------|
+| Yo soy Alex. | I am Alex. |
+| Yo soy español. | I am Spanish. |
+| Yo soy de España. | I am from Spain. |
+| Él es profesor. | He is a professor. |
+| Tú eres bonito/a. | You are beautiful. |
+| Es importante trabajar. | It is important to work. |
+| La fiesta es en el club. | The party is in the club. |
+| La fiesta es a las seis. | The party is at six. |
+| Es viernes. | It is Friday. |
+| Es la una de la tarde. | It is one in the afternoon. |
+| Son las dos de la tarde. | It is two in the afternoon. |
+| Son las tres / cuatro de la tarde. | It is three / four in the afternoon. |
+
+## Notes & Gotchas
+- The classic schoolroom rule "ser = permanent, estar = temporary" is a useful heuristic but not the deepest explanation. The author prefers: **ser = factual statements**.
+- Physical traits go with *ser* because they're treated as factual identity (*Él es alto* — He is tall).
+- Be careful: *es* (he/she/it is) and *eres* (you are) sound similar — *eres* is for *tú*.
+- Even time of day is treated as a factual statement: *Son las dos de la tarde* — "It is (factually) two in the afternoon right now."