feat: offer non-travelling applicant choice only on selected travels

src/Form/Model/BookingDto.php

@@ -193,6 +193,26 @@ class BookingDto
         return $this->participants[$index] ?? null;
     }
 
+    /**
+     * Ends a split: the applicant takes the participant[0] slot back and travels again.
+     *
+     * The traveller who held the slot is dropped; only the room assignment carries over,
+     * the mirror image of what the split left behind.
+     */
+    public function restoreTravellingApplicant(): void
+    {
+        $restored = $this->applicant;
+
+        if (null !== $restored) {
+            $restored->index = 0;
+            $restored->assignedRoomId = ($this->participants[0] ?? null)?->assignedRoomId;
+            $this->participants[0] = $restored;
+        }
+
+        $this->applicant = null;
+        $this->applicantTravels = true;
+    }
+
     /**
      * Whether participant[0] is also the applicant.
      *