fix: import unpublished exam rooms and add opt-in school HTML feedback

mobile/test/school/undergraduate_timetable_adapter_test.dart

@@ -9,6 +9,27 @@ import 'package:hepan_everyday/data/schedule_file_import.dart';
 import 'package:hepan_everyday/domain/school_identity.dart';
 
 void main() {
+  test('missing course fields identify the failing field without disclosing values', () {
+    const base =
+        'new TaskActivity("T", "教师", "C", "课程(C.01)", "R", "教室", "010"); '
+        'index=0*unitCount+0;table0.activities[index][table0.activities[index].length]=activity;';
+    for (final entry in {
+      'teacher_missing': base.replaceFirst('"教师"', '""'),
+      'room_missing': base.replaceFirst('"教室"', '""'),
+      'course_sequence_invalid': base.replaceFirst('课程(C.01)', '课程'),
+    }.entries) {
+      expect(
+        () => parseActivityData(entry.value, unitCount: 12),
+        throwsA(
+          isA<UndergraduateActivityException>().having(
+            (e) => e.code,
+            'reason',
+            entry.key,
+          ),
+        ),
+      );
+    }
+  });
   test('unrecognized activity writes and incomplete declarations reject the entire timetable', () {
     const valid =
         'activity = new TaskActivity("T", "教师", "C", "课程(C.01)", "R", "教室", "010"); '