Redesign marketing homepage

Rework the landing page: a For humans / For agents hero toggle (Run locally
primary CTA plus a copyable agent-setup prompt), an interactive context
efficiency demo (connect services and watch the system prompt balloon into
thousands of tools versus one execute tool), a pricing section, reworked
Pick your path cards (Cloud / Desktop / CLI), a Backed by Y Combinator badge,
and copy, CTA, and layout cleanups throughout.

Author: RhysSullivan