Block Kit Help the developer build a rich Block Kit layout. If is exactly , , or , treat it as the target surface. Otherwise (including if it's empty or any other value), ignore it and determine the surface in Step 1. This skill walks through surface selection, layout planning, JSON generation, and validation. Block types, elements, and fields come from the live docs (see Source of Truth below) — discover them and read each component's schema there, never from memory. Common Block Kit mistakes (and why): A few errors recur often enough to flag up front. Most others are caught by in Step 5, so…