Storyline: per-chapter DM notes

Each chapter page gets a collapsible "Chapter notes" card at the top — a
free-text log the DM fills during play (the story the party tells after
the Crooked Goose, names given to NPCs, threads for next time). Saved
per chapter slug with a "saved <timestamp>" marker, same shape as the
Enemy/NPC game-notes field.

New: ChapterNote entity (slug-keyed, unique) + repository findOrCreate(),
ChapterNoteType form, chapter_note table migration (ENGINE = InnoDB
pinned). The storyline chapter route now also accepts POST to save.

Chapters stay hand-written Twig; only the mutable notes live in the DB.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/Controller/StorylineController.php

@@ -2,7 +2,11 @@
 
 namespace App\Controller;
 
+use App\Form\ChapterNoteType;
+use App\Repository\ChapterNoteRepository;
+use Doctrine\ORM\EntityManagerInterface;
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\Routing\Attribute\Route;
 use Symfony\Component\Security\Http\Attribute\IsGranted;
@@ -46,13 +50,27 @@ class StorylineController extends AbstractController
         ]);
     }
 
-    #[Route('/storyline/{slug}', name: 'app_storyline_chapter', requirements: ['slug' => '[a-z0-9-]+'], methods: ['GET'])]
-    public function chapter(string $slug): Response
+    #[Route('/storyline/{slug}', name: 'app_storyline_chapter', requirements: ['slug' => '[a-z0-9-]+'], methods: ['GET', 'POST'])]
+    public function chapter(string $slug, Request $request, ChapterNoteRepository $notes, EntityManagerInterface $em): Response
     {
         if (!isset(self::CHAPTERS[$slug])) {
             throw $this->createNotFoundException('No such storyline chapter.');
         }
 
+        $note = $notes->findOrCreate($slug);
+        $form = $this->createForm(ChapterNoteType::class, $note);
+        $form->handleRequest($request);
+
+        if ($form->isSubmitted() && $form->isValid()) {
+            if (null === $note->getId()) {
+                $em->persist($note);
+            }
+            $em->flush();
+            $this->addFlash('success', 'Chapter notes saved.');
+
+            return $this->redirectToRoute('app_storyline_chapter', ['slug' => $slug]);
+        }
+
         $slugs = array_keys(self::CHAPTERS);
         $pos = array_search($slug, $slugs, true);
 
@@ -60,6 +78,8 @@ class StorylineController extends AbstractController
             'chapters' => self::CHAPTERS,
             'slug' => $slug,
             'chapter' => self::CHAPTERS[$slug],
+            'note' => $note,
+            'form' => $form,
             'prev' => $pos > 0 ? $slugs[$pos - 1] : null,
             'next' => $pos < \count($slugs) - 1 ? $slugs[$pos + 1] : null,
         ]);