fix: derive contingent change signal from the sync diff

src/Service/ContingentSnapshotManager.php

@@ -53,6 +53,10 @@ class ContingentSnapshotManager
 
         $state = $this->syncStateRepository->findOneByAccommodation($accommodation) ?? new ContingentSyncState($accommodation);
 
+        // Read before recordSuccess() moves it: days beyond the horizon the previous run reached
+        // are the window growing, not the contingent situation changing.
+        $previousHorizonTo = $state->getHorizonTo();
+
         try {
             $calendar = $this->contingentsClient->getContingentCalendar(
                 $hotelCode,
@@ -72,6 +76,7 @@ class ContingentSnapshotManager
         }
 
         $added = 0;
+        $extended = 0;
         $updated = 0;
         $seen = [];
 
@@ -102,7 +107,12 @@ class ContingentSnapshotManager
                     ->setDate($date);
 
                 $this->entityManager->persist($day);
-                ++$added;
+
+                if (null !== $previousHorizonTo && $date > $previousHorizonTo) {
+                    ++$extended;
+                } else {
+                    ++$added;
+                }
             } elseif ($day->getStatus() === $entry->status) {
                 continue;
             } else {
@@ -124,26 +134,21 @@ class ContingentSnapshotManager
         $this->entityManager->flush();
 
         $now = CarbonImmutable::now()->toDateTimeImmutable();
-        $hash = $this->fingerprint($accommodation);
-        $changed = $hash !== $state->getContentHash();
+
+        // The diff is the change signal. A digest of the stored snapshot cannot be one: the window
+        // rolls forward a day at a time, so every digest would cover a different span than the one
+        // it is compared against and every run would report a change.
+        $changed = $added > 0 || $updated > 0 || $removed > 0;
 
         if ($changed) {
-            $state->setContentHash($hash)->setChangedAt($now);
+            $state->setChangedAt($now);
         }
 
         $state->recordSuccess($now, $dateTo);
         $this->entityManager->persist($state);
         $this->entityManager->flush();
 
-        return ContingentSyncResult::synced($changed, $added, $updated, $removed);
-    }
-
-    /**
-     * sha256 over the accommodation's complete stored snapshot, contingent status only.
-     */
-    public function fingerprint(Accommodation $accommodation): string
-    {
-        return hash('sha256', implode('|', $this->dayRepository->findStatusFingerprintParts($accommodation)));
+        return ContingentSyncResult::synced($changed, $added, $extended, $updated, $removed);
     }
 
     private function recordFailure(ContingentSyncState $state, string $hotelCode, string $error): ContingentSyncResult