New docs page covering install pointers, binary names the daemon scans
for, and basic auth notes for all 11 supported AI coding tools. EN +
zh-Hans, registered under "How agents run" in the docs sidebar.
The onboarding "no agent runtime found" empty state now shows an
"Install an agent runtime →" link that opens the new doc, so users have
a discoverable path beyond "skip" and "join waitlist".
Co-authored-by: multica-agent <github@multica.ai>