Move chunk builder into SetupPage via useChunkBuilder

- The setup form, active chapter tab, verse range selection, typed/bulk/
  cross-chapter chunk creation, reorder, and delete move out of App.
- Setup now opens on the chapter holding the chunk last studied (e.g.
  after Back to Chunks), and the Add Chapter form suggests the chapter
  after the project's last one instead of repeating the current one.
- openNewProject/goHome/resume/import no longer reset setup state by hand;
  SetupPage starts fresh each time it opens.
- Tests: add-chapter default, Back to Chunks chapter.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/pages/SetupPage.jsx

@@ -1,4 +1,5 @@
 import { useApp } from '../context/AppContext.js';
+import { useChunkBuilder } from '../hooks/useChunkBuilder.js';
 import ProjectHeader from '../components/ProjectHeader.jsx';
 import { useAvailableTranslations } from '../hooks/useAvailableTranslations.js';
 import { bookOptions, formatChunkReference } from '../utils/bibleUtils.jsx';
@@ -81,8 +82,8 @@ function SetupForm({ setup, availableTranslations, titleEdited, loadingChapter,
 }
 
 export default function SetupPage() {
+  const { project, setProject, allChunks, updateProject, setCurrentPage } = useApp();
   const {
-    project,
     setup,
     titleEdited, setTitleEdited,
     activeChapterIndex, setActiveChapterIndex,
@@ -99,7 +100,6 @@ export default function SetupPage() {
     loadingChapter,
     errorMessage,
     statusMessage,
-    allChunks,
     handleSetupField,
     handleLoadChapter,
     beginStudying,
@@ -109,8 +109,7 @@ export default function SetupPage() {
     addClickSpanChunk,
     moveChunk,
     deleteChunk,
-    updateProject,
-  } = useApp();
+  } = useChunkBuilder({ project, setProject, updateProject, allChunks, setCurrentPage });
   const availableTranslations = useAvailableTranslations();
 
   const chapterTabs = project?.chapters ?? [];