fix(labs): name a merge in the owner's activity feed and toast it through the outcome module

A merge by a record manager now reads as its own sentence in the owner's
activity feed, the merged toast goes through the written-outcome toast,
and the export test doubles carry the alias and merge tables.

src/lib/record-activity/activity-verb.ts

@@ -179,6 +179,8 @@ export function recordActivityVerbLine(
       return t("recordSharing.activityVerb.biomarkerUpdate", { name });
     case "biomarker.delete":
       return t("recordSharing.activityVerb.biomarkerDelete", { name });
+    case "labs.biomarker.merge":
+      return t("recordSharing.activityVerb.biomarkerMerge", { name });
 
     case "allergy.update":
       return t("recordSharing.activityVerb.allergyUpdate", { name });