AI chat on Waku and Astro

aiPlugin() and mcpPlugin() work on Waku and Astro, and fumapress is no longer a peer dependency.
The built-in UI docks the chat, with a floating "Ask AI" button.
The chat reaches layouts as their aiChat prop through useLayoutProps(), so a custom layout docks it by spreading useLayoutProps(). Docs and Notebook layouts show a floating "Ask AI" button, Glass and Spacious their own.
Removed AIChatLayout, and AIChat takes the endpoint as its api prop.
AI search indexes the pages of every plugin with page text, like OpenAPI pages.
/api/ai answers 400 to messages the UI never sends: system messages and parts like files, which the server would download.