Docs: Audit Subtitle/Opening Paragraph Redundancy Across Docs

[!NOTE] Triage estimate — cycle priority and story points were assigned during an AI-assisted planning pass and are rough first guesses. Confirm or adjust when you pick this up.

Context

Several docs pages have a description subtitle and an opening paragraph that do the same work. The subtitle doesn't add value when the first sentence restates it.

Feedback from @davekiss:

There are several moments in the docs where I feel that the page, subheader, and the first sentences on the page are basically doing the same work. They're describing the same thing. It makes it feel like the subheader doesn't really have much of a purpose, and you might be better off considering removing it, only keeping it for SEO purposes in meta tags. We face this too on the Mux docs sometimes, just a thought. Alternatively revisit the first sentences so it's doing different work than the subheadline.

Proposal

Audit docs pages and either:

• Differentiate the opening paragraph from the subtitle so each does distinct work, or
• Hide the subtitle visually and keep it only in meta tags for SEO