Standardize title capitalization to sentence case

[beran-t]

Summary

Standardizes all documentation titles, headings, and component titles to sentence case — only the first word and proper nouns/acronyms are capitalized.

Why sentence case?

• Consistency — the docs were ~65% sentence case already, with Title Case scattered mostly in the template section and agent pages. This aligns everything to the dominant convention.
• Easier to maintain — sentence case has one simple rule (capitalize first word + proper nouns). Title Case requires judgment calls on words like "with", "is", "and" — different style guides disagree, and inconsistencies like "User And Workdir" were already creeping in.
• Industry standard for dev docs — Stripe, Vercel, Next.js, Supabase, Tailwind, and most modern developer documentation use sentence case.

[beran-t]

Re: BYOC — agree to keep "BYOC (Bring Your Own Cloud)" capitalized. It's the proper name behind the acronym, and the body text already uses the capitalized form. Recommend reverting the title and sidebarTitle changes in docs/byoc.mdx back to the original casing.

[matthewlouisbrockman]

styling change, seems fine. possibly worth adding linter if care about this moving forward (would probably just stick a package.json in root and add linter there)