[ENG-601] feat: allow planned encounters (w/ future start date) to transition to cancelled/discontinued/entered in error

src/components/Questionnaire/QuestionTypes/EncounterQuestion.tsx

@@ -135,13 +135,15 @@ export function EncounterQuestion({
   });
 
   useEffect(() => {
+    const isStartDateInFuture =
+      encounter.period.start && new Date(encounter.period.start) > new Date();
+
     if (
       encounter.status === EncounterStatus.DISCHARGED ||
-      encounter.status === EncounterStatus.COMPLETED ||
-      encounter.status === EncounterStatus.CANCELLED ||
       encounter.status === EncounterStatus.DISCONTINUED ||
-      encounter.status === EncounterStatus.ENTERED_IN_ERROR
+      encounter.status === EncounterStatus.COMPLETED
     ) {
+      // Always set end date — if start is in the future, BE will reject it
       if (!encounter.period.end) {
         handleUpdateEncounter({
           period: {
@@ -150,6 +152,28 @@ export function EncounterQuestion({
           },
         });
       }
+    } else if (
+      encounter.status === EncounterStatus.CANCELLED ||
+      encounter.status === EncounterStatus.ENTERED_IN_ERROR
+    ) {
+      if (isStartDateInFuture) {
+        // Valid transition from future encounters — don't set end date
+        if (encounter.period.end) {
+          handleUpdateEncounter({
+            period: {
+              ...encounter.period,
+              end: undefined,
+            },
+          });
+        }
+      } else if (!encounter.period.end) {
+        handleUpdateEncounter({
+          period: {
+            ...encounter.period,
+            end: new Date().toISOString(),
+          },
+        });
+      }
     } else {
       handleUpdateEncounter({
         period: {