Onboard business-idea-eval

This plugin keeps the user's actual idea data outside the plugin install directory. On first run, capture two things:

1. Workspace path — where ideas/<idea-slug>/ directories will live. Suggest ~/Documents/business-ideas/ or a dedicated git repo under ~/repos/. Confirm with the user before writing.
2. User context — short prose answering: background and domain expertise; current capital availability (bootstrap / small / VC-track); risk appetite; geography (defaults to user's locale); strong preferences (e.g. "B2B SaaS only", "open to hardware"). This is loaded into every lens analysis so outputs are calibrated to the user, not generic.

Steps