Onboarding: header and connect panel

[talissoncosta]

Part of #7737. Extracts the top of the single-page flow from OnboardingSinglePage.tsx into prop-driven components with stories.

Scope

• Header: editable org / project chips + flag rename.
• Connect panel: manual SDK tab (chips + "More" + snippets) and "Connect with AI" tab (zero-auth prompt with real env key + flag).
• Stories for both (variant states; light + dark for snippets).

Done when

• Both are standalone prop-driven components rendered by the page.
• Real env key + flag in snippets/prompt; nothing faked.
• Stories cover the states.