feat: select school terms and smooth refractive Dock motion

mobile/lib/app/app_controller.dart

@@ -9,6 +9,7 @@ import '../services/calendar_service.dart';
 import '../domain/schedule_engine.dart';
 import '../data/demo_schedule.dart';
 import '../domain/exam_schedule.dart';
+import '../domain/school_term.dart';
 
 class AppController extends ChangeNotifier {
   AppController(this.store, this.notifications, this.calendar, this.clock);
@@ -145,6 +146,11 @@ class AppController extends ChangeNotifier {
     await _save(
       snapshot.copyWith(
         courses: draft.courses,
+        schoolTerm: draft.schoolTerm,
+        clearExams: _differentTerm(draft.schoolTerm),
+        settings: _differentTerm(draft.schoolTerm)
+            ? snapshot.settings.copyWith(clearSemester: true)
+            : snapshot.settings,
         importMetadata: ImportMetadata(
           source: draft.source,
           importedAt: clock(),
@@ -177,8 +183,29 @@ class AppController extends ChangeNotifier {
   });
   Future<void> applyExams(ExamSchedule value) => _run(() async {
     final validated = ExamSchedule.fromJson(value.toJson());
-    await _save(snapshot.copyWith(examSchedule: validated));
+    final term = SchoolTerm(int.parse(validated.termId));
+    final changed = _differentTerm(term);
+    await _save(
+      snapshot.copyWith(
+        examSchedule: validated,
+        schoolTerm: term,
+        courses: changed ? [] : null,
+        clearMetadata: changed,
+        settings: changed
+            ? snapshot.settings.copyWith(clearSemester: true)
+            : null,
+      ),
+    );
+    if (changed) {
+      isDemo = false;
+      await _reconcile();
+    }
   });
+  bool _differentTerm(SchoolTerm? next) =>
+      next != null &&
+      ((snapshot.schoolTerm != null && snapshot.schoolTerm != next) ||
+          (snapshot.schoolTerm == null &&
+              (snapshot.courses.isNotEmpty || snapshot.examSchedule != null)));
   Future<void> clearExams() => _run(() async {
     await _save(snapshot.copyWith(clearExams: true));
   });