[Experience] Ship outcome-first onboarding and human-readable team previews

[pate0304]

Outcome

Show users what Codesemble found, what it can generate, why every agent exists, and what will change before asking implementation details.

Acceptance criteria

• First useful proposal appears after at most two user questions.
• Project stage, runtime capabilities, models, tools, and initial team size are inferred when possible.
• Users can customize teams in natural language.
• Every role displays evidence, mission, scope, sandbox, model, cost implication, deliverables, and example tasks.
• Roles versus workers and project versus global config are understood by at least 90 percent of usability participants.
• Update and rollback present human-readable deltas and recovery.