Give the README the shape aimock's has (#6)

A wall of prose asks a visitor to read before they can tell whether this is
for them. Lead with one sentence, the diagram, and the badges that say it
builds, then a table of surfaces and a scannable feature list.

Two sections were saying the same thing three times over: a capability table,
a feature list, and a components/MCP/skills section beneath both. Keep the
feature list, drop the other two, and let docs/ carry the detail.