List all projects for a claim with nested activities.

source selects the data source. When omitted, the claim's discovery_methodology decides:

• NULL (default) -> legacy (read from the original AURD tables via _build_project_list_response).
• non-null (e.g. "activity-map.v1") -> activity-map (read from activity_map_* tables via _build_project_list_response_from_activity_map).

Pass an explicit ?source=legacy|activity-map to override the claim setting (admin dogfooding / dev testing). The status_filter argument is mapped to the activity-map builder's status_filter semantics (active / all); None becomes active.

Note: projects and activities with status='merged' (soft-deleted by a reverse-mergeable merge) are always filtered out of this response. Use GET …/projects/merged and GET …/activities/merged to enumerate them; ?status=merged here will return an empty list.