docs: connect MCP architecture choice to first dataset setup

[gregagi]

Summary

• Help quickstart readers distinguish agent-owned workflow rows from direct access to production tables.
• Link the existing MCP architecture guide to the first-dataset walkthrough and task-board example.
• Preserve current titles, routes, access behavior and source-of-truth boundaries. Record the content edit date and changelog.

Purpose

Make the existing discovery-to-setup path actionable without creating a duplicate keyword page. Acquisition and activation effects remain unmeasured.

Checks and authority

• Current main, all existing content-ledger entries and open PRs checked for reservations.
• Seven focused public HTTP destinations returned 200; the docs hub resolves to quickstart. Existing destination canonicals and indexability checked.
• Product claims checked against PRODUCT.md and existing setup documentation; git diff --check passed.
• Content-only publishing exception authorized by Rasul 2026-09-09: mandatory test/review waits waived, not reported as passed. No code or technical configuration changes.
• Content sitemap intentionally omits lastmod for docs; this change does not introduce build-time dates.
• Deployment and production HTML/Markdown verification follow merge. No ranking or conversion result claimed.