fix: typos, mislabeled 3a/3c progress, and stale README bounds

[Chessing234]

Summary

• Fix Gyamarti → Gyarmati in the README table and on constants/3a.md.
• Recent progress listed Griego’s $C_{3a}$/$C_{3c}$ updates as upper bounds with $\le$; those values are lower bounds (and already appear in the lower-bound tables). Relabel accordingly.
• Sync README best-bound cells with the constant pages for $C_{3a}$, $C_{4a}$, $C_{42}$, $C_{50}$, and $C_{59}$ (including the unverified $0.6906538*$ upper bound for $C_{42}$).
• Small page fixes: Aca Math. → Acta Math. ($C_{42}$); unmatched parenthesis / $\lambda_{\max}(H_G)$ in the $C_{50}$ definition; contribution-notes heading on $C_{3c}$; reference-list spacing on $C_{4a}$ and $C_{8a}$; missing space after | for $C_{26b}$ in the README.

Independent of open bound-improvement PRs (#128, #134, #135). Does not touch $C_{21}$/$C_{71}$ README cells covered by #128.

Test plan

• Compare updated README cells against constants/{3a,4a,42a,50a,59a}.md bound tables
• Confirm Gyarmati spelling matches [GHR2007] authorship
• Confirm recent-progress line uses $\ge$ and “lower bounds”
• Spot-check rendered markdown for $C_{50}$ definition and $C_{3c}$ contribution notes
• Confirm GitHub Pages build succeeds

Made with Cursor