Preserve courses with pending rooms and report precise graduate import errors

mobile/test/school/undergraduate_timetable_adapter_test.dart

@@ -7,6 +7,7 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:hepan_everyday/features/school/undergraduate/timetable_adapter.dart';
 import 'package:hepan_everyday/data/schedule_file_import.dart';
 import 'package:hepan_everyday/domain/school_identity.dart';
+import 'package:hepan_everyday/domain/course.dart';
 
 void main() {
   test('missing course fields identify the failing field without disclosing values', () {
@@ -15,7 +16,6 @@ void main() {
         '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(
@@ -51,6 +51,24 @@ void main() {
   String fixture() =>
       File('test/fixtures/school/undergraduate-timetable.html')
           .readAsStringSync();
+  test('missing room retains every scheduled occurrence and clearly marks it pending', () {
+    final original = UndergraduateTimetableAdapter.extract(fixture(), uri);
+    final draft = UndergraduateTimetableAdapter.extract(
+      fixture().replaceFirst('"教室1"', '""'),
+      uri,
+    );
+    Set<String> occurrences(Iterable<Course> courses) => <String>{
+      for (final c in courses)
+        for (final w in c.weeks)
+          for (var p = c.startPeriod; p <= c.endPeriod; p++)
+            '${c.courseCode}/${c.teacher}/${c.weekday}/$p/$w',
+    };
+    expect(occurrences(draft.courses), occurrences(original.courses));
+    final pending = draft.courses.where((c) => c.room == '教室待定');
+    expect(pending, isNotEmpty);
+    expect(pending.every((c) => c.notes.contains('学校未提供教室')), isTrue);
+    expect(draft.courses.any((c) => c.room == '教室2'), isTrue);
+  });
   test('undergraduate activity data preserves teachers rooms weeks and period twelve', () {
     final draft = UndergraduateTimetableAdapter.extract(fixture(), uri);
     expect(draft.schoolTerm!.id, 523);