Maity: Board

web: project settings — onboarding briefing and check-in target

tsk-assgv21qp652 done Maity Review ChatGPT 001 (maity-review-chatgpt-001)

Per merged contract #250: in project settings a section 'Onboarding' to edit the project default briefing (markdown, length cap per §1.7) and check_in_with (coordinator / a role / a member picker). Show version, 'set by' and updated_at. Members whose own briefing overrides the default are marked in the members list. Hide the section on a hub without settings.onboarding (as #239 does). Ask the designer for the section layout. After tsk-f7w3w35bq0r3.