fix(persist): persist new books on create

A freshly created book lived only in memory until the first edit, so
quitting beforehand lost it and it never appeared in the library. Save
it to disk on creation via a shared createAndOpenBook used by both the
Library card and the New Book menu action.

Claude-Session: https://claude.ai/code/session_01RzTWrLiy4zGuw2hZSQGamk

src/App.tsx

@@ -5,7 +5,7 @@ import { Library } from "./components/Library";
 import { EditorView } from "./components/EditorView";
 import { useBook } from "./store/useBook";
 import { isDesktop } from "./ipc";
-import { newBook, saveBook } from "./library";
+import { createAndOpenBook, saveBook } from "./library";
 import { runExport } from "./export/run";
 import { checkForUpdates } from "./updater";
 
@@ -18,7 +18,7 @@ function App() {
     checkForUpdates(true);
     const unlisten = listen<string>("menu-action", (event) => {
       const state = useBook.getState();
-      if (event.payload === "new-book") state.openBook(newBook());
+      if (event.payload === "new-book") createAndOpenBook(state.openBook, state.setNotice);
       else if (event.payload === "export-pdf") runExport("pdf");
       else if (event.payload === "export-epub") runExport("epub");
       else if (event.payload === "check-updates") checkForUpdates(false);

src/components/Library.tsx

@@ -1,5 +1,5 @@
 import { useEffect, useState } from "react";
-import { type BookSummary, deleteBook, exampleBook, listBooks, loadBook, newBook, saveBook } from "../library";
+import { type BookSummary, createAndOpenBook, deleteBook, exampleBook, listBooks, loadBook, saveBook } from "../library";
 import type { Book } from "../model/book";
 import { importEpub } from "../import/epub";
 import { isDesktop } from "../ipc";
@@ -64,7 +64,7 @@ export function Library({ onOpen }: { onOpen: (book: Book) => void }) {
     <div className="library">
       <header className="library-head" data-tauri-drag-region />
       <div className="shelf">
-        <button className="card card-action" onClick={() => onOpen(newBook())}>
+        <button className="card card-action" onClick={() => createAndOpenBook(onOpen, setNotice)}>
           <Icon d="M12 5v14M5 12h14" size={20} />
           <span>New book</span>
         </button>

src/library.ts

@@ -35,3 +35,18 @@ export function newBook(): Book {
 export function exampleBook(): Book {
   return starterBook();
 }
+
+export async function createAndOpenBook(
+  open: (book: Book) => void,
+  onError?: (message: string) => void,
+): Promise<void> {
+  const book = newBook();
+  if (isDesktop) {
+    try {
+      await saveBook(book);
+    } catch (e) {
+      onError?.(`Could not create book: ${e}`);
+    }
+  }
+  open(book);
+}