fix: proofread Set Theory I part

[vEnhance]

This PR proofreads the Set Theory I: ZFC, Ordinals, and Cardinals part (issue #315), covering:

• tex/set-theory/zorn-lemma.tex
• tex/set-theory/zfc.tex
• tex/set-theory/ordinal.tex
• tex/set-theory/cardinal.tex

All the substantive mathematics checks out — the bijection tables ($\omega+1 \approx \omega$, $\omega \approx \omega^2$), ordinal/cardinal arithmetic constructions, the von Neumann hierarchy computations ($V_3 = {0,1,2,{1}}$), and the $\kappa \cdot \kappa = \kappa$ proof with its $<_{\max}$ enumeration table all verify correctly.

Only a few minor issues were found and fixed:

• zfc.tex: stray comma in the Cantor diagonal exercise — "Show that if, $\iota$ exists," → "Show that if $\iota$ exists,".
• zorn-lemma.tex: grammatical slip in the Cauchy functional-equation problem — "It's possible for $f$ is nonconstant …" → "It's possible that $f$ is nonconstant …", matching the phrasing of the adjacent item.
• cardinal.tex: stray space inside a subscript, $\aleph_ 0$ → $\aleph_0$.
• cardinal.tex: the example titled "Beth fixed point" actually concerns the aleph function ($\kappa = \aleph_{\aleph_{\aleph_\ddots}}$, so $\kappa = \aleph_\kappa$), not the beth function; retitled to "Aleph fixed point".

No large mathematical errors were found.

🤖 Generated with Claude Code

https://claude.ai/code/session_01JYnQwxZGUNjX354EBzZoRN

---

Generated by Claude Code