Compare only resolved members when planning speaker and instructor changes

Without a member group the import stores an empty speaker list, but the
planner turned every unresolved name into ID 0 and flagged the event as
changed on each upload. With a member group set, the preview now also
reports the change when instructor or speakers will be created on apply.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/Import/ImportPlanner.php

@@ -126,12 +126,20 @@ class ImportPlanner
 
         $cancelled = WkState::isCancelled($data['wkState']);
 
-        // Personen (nur nachschlagen; angelegt wird beim Anwenden)
+        // Personen (nur nachschlagen; angelegt wird beim Anwenden). Namen ohne Mitglied werden nur dann zu
+        // Mitgliedern, wenn im Kalender eine Mitgliedergruppe gesetzt ist; sonst speichert der Import sie nicht.
         $instructorId = '' !== $row->instructorName ? $this->memberResolver->findId($row->instructorName) : null;
         $speakerIds = [];
+        $unresolvedSpeakers = [];
 
         foreach ($row->speakerNames as $name) {
-            $speakerIds[] = $this->memberResolver->findId($name);
+            $id = $this->memberResolver->findId($name);
+
+            if (null === $id) {
+                $unresolvedSpeakers[] = $name;
+            } else {
+                $speakerIds[] = $id;
+            }
         }
 
         if (null === $existing) {
@@ -185,14 +193,16 @@ class ImportPlanner
         }
 
         $existingInstructor = (int) $existing['wkInstructor'];
+        $instructorWillBeCreated = $calendar->instructorGroup > 0 && '' !== $row->instructorName && null === $instructorId;
 
-        if (('' !== $row->instructorName || $existingInstructor > 0) && $existingInstructor !== (int) $instructorId) {
+        if ($existingInstructor !== (int) $instructorId || $instructorWillBeCreated) {
             $changes['wkInstructor'] = [$this->memberName($existingInstructor), $row->instructorName];
         }
 
         $existingSpeakers = array_map(intval(...), StringUtil::deserialize($existing['wkSpeakers'] ?? null, true));
+        $speakersWillBeCreated = $calendar->speakerGroup > 0 && [] !== $unresolvedSpeakers;
 
-        if ($existingSpeakers !== array_map(static fn (int|null $id): int => (int) $id, $speakerIds) && ([] !== $existingSpeakers || [] !== $row->speakerNames)) {
+        if ($existingSpeakers !== $speakerIds || $speakersWillBeCreated) {
             $changes['wkSpeakers'] = [implode(', ', array_values($this->memberResolver->namesByIds($existingSpeakers))), implode(', ', $row->speakerNames)];
         }