fix(web): pass full ProseMirror doc to editor, not bare array

WritingView passed chapter.doc.content (a bare ProseMirror node array)
as the editor content, which made EditorState.create build a doc node
with an undefined type, throwing 'Cannot read properties of undefined
(reading schema)' and unmounting the write view. Pass the full doc
object ({ type: 'doc', content }) on init and on setContent sync.

Add editor regression tests covering schema instantiation, node
registration, and doc-content round-trip.

apps/web/src/components/WritingView.tsx

@@ -57,7 +57,10 @@ export function WritingView({ onChapterChange }: WritingViewProps) {
   const projectId = project?.id ?? null;
 
   const { editor } = usePubScriptEditor({
-    ...(chapter ? { content: chapter.doc.content } : {}),
+    // Pass the full ProseMirror doc (`{ type: "doc", content }`), not the bare
+    // `content` array — TipTap/ProseMirror cannot build a doc node from a bare
+    // array, which would leave `doc.type` undefined and crash `EditorState.create`.
+    ...(chapter ? { content: chapter.doc } : {}),
     onUpdate: (ed) => {
       if (!chapter || !projectId) return;
       const json = ed.getJSON().content;
@@ -76,7 +79,7 @@ export function WritingView({ onChapterChange }: WritingViewProps) {
   // from re-entering onUpdate (which would otherwise re-save what we just loaded).
   useEffect(() => {
     if (!editor || !chapter) return;
-    editor.commands.setContent(chapter.doc.content, { emitUpdate: false });
+    editor.commands.setContent(chapter.doc, { emitUpdate: false });
     editor.commands.focus();
   }, [editor, chapter?.id]);