Onboarding: intent gate, hierarchy orientation, and persona-specific flows

The memsprout onboarding guide now opens with an intent gate that identifies whether you are a team lead setting up a new Space, a team member who was invited to an existing one, or an individual building a personal vault — and routes the entire flow accordingly. Before any structural question is asked, a brief Spaces ▸ Topics ▸ Memories hierarchy diagram is shown so every choice makes sense. Team leads get a focused team-and-project discovery step that proposes three to five Spaces (team-axis first), a personal-vs-org truth check at every candidate memory (under-share by default), and a wire-in step that leads with the spread value and lets them decide without pressure. Team members are first checked for their role in the invited Space — viewers get orientation and assistant wiring only, with no contribution prompts; editors and owners get the full flow including an offer to contribute org-worthy knowledge they hold. Individuals get a personal vault that prefers the General topic and proposes a handful of starter memories mined from their recent areas of focus rather than starting blank. The gather step now explicitly mines the agent's own stored memories as its first lane across all personas.