test: parse NDJSON documents in getTaskDocuments test

Show how to access individual documents from the stream by
splitting NDJSON lines, decoding each, and asserting structure.
Fixes phpstan alreadyNarrowedType error by removing redundant
assertInstanceOf check.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mvanhorn

tests/Endpoints/TasksTest.php

@@ -14,7 +14,6 @@
 use Meilisearch\Endpoints\Indexes;
 use Meilisearch\Exceptions\ApiException;
 use Meilisearch\Http\Client;
-use Psr\Http\Message\StreamInterface;
 use Tests\TestCase;
 
 final class TasksTest extends TestCase
@@ -59,9 +58,13 @@ public function testGetTaskDocumentsClient(): void
 
         $stream = $this->client->getTaskDocuments($task->getTaskUid());
 
-        self::assertInstanceOf(StreamInterface::class, $stream);
-        $content = (string) $stream;
-        self::assertNotEmpty($content);
+        // Parse NDJSON: each line is a separate JSON document
+        $lines = array_filter(explode("\n", (string) $stream), fn (string $line) => '' !== trim($line));
+        self::assertNotEmpty($lines, 'Stream should contain at least one NDJSON line');
+
+        $documents = array_map(fn (string $line) => json_decode($line, true, 512, \JSON_THROW_ON_ERROR), $lines);
+        self::assertNotEmpty($documents);
+        self::assertArrayHasKey('id', $documents[0], 'Each document should have an id field');
     }
 
     public function testGetAllTasksClient(): void