New "partial_fill" execution type on activity trade details

Broker API

Adds partial_fill to the execution_type enum on the ActivityV2DetailTRD schema. Activity events already report partial_fill for partially filled trades; the API description now documents it. Existing enum values (fill, trade_correct, trade_bust) are unchanged.

Affected Endpoints

• GET /v2beta1/events/activities
• GET /v2beta1/accounts/{account_id}/events/activities/{event_id}