feat(fonts): add bundled fonts and per-book font model

Add EB Garamond, Lora, Source Serif 4, and Fraunces (OFL variable
fonts) and a font catalog with body/heading pairings. Store the chosen
fonts per book in BookSettings.fonts, defaulting to Literata so existing
books are unchanged.

src/import/epub.ts

@@ -2,6 +2,7 @@ import { invoke } from "@tauri-apps/api/core";
 import { open } from "@tauri-apps/plugin-dialog";
 import type { JSONContent } from "@tiptap/core";
 import { type Book, type BookMetadata, type Chapter, type Cover, createCover } from "../model/book";
+import { DEFAULT_FONTS } from "../model/fonts";
 
 export interface RawFile {
   path: string;
@@ -515,7 +516,7 @@ export function filesToBook(files: RawFile[], fallbackName = "Imported book"): B
     id: crypto.randomUUID(),
     metadata,
     theme: "quiet-press",
-    settings: { trim: "6x9", bleed: true },
+    settings: { trim: "6x9", bleed: true, fonts: DEFAULT_FONTS },
     cover: findCover(opf, manifest, byPath),
     chapters,
   };

src/model/book.ts

@@ -1,4 +1,5 @@
 import type { JSONContent } from "@tiptap/core";
+import { type BookFonts, DEFAULT_FONTS } from "./fonts";
 
 export type TrimSize = "6x9" | "5.5x8.5" | "5x8" | "a5";
 export type FigurePlacement = "inline" | "full-width" | "full-page" | "float-top";
@@ -24,6 +25,7 @@ export interface BookMetadata {
 export interface BookSettings {
   trim: TrimSize;
   bleed: boolean;
+  fonts: BookFonts;
 }
 
 export type CoverKind = "default" | "image";
@@ -149,14 +151,14 @@ export function createCover(): Cover {
 }
 
 const DEFAULT_METADATA: BookMetadata = { title: "Untitled", subtitle: "", author: "", isbn: "", language: "en" };
-const DEFAULT_SETTINGS: BookSettings = { trim: "6x9", bleed: true };
+const DEFAULT_SETTINGS: BookSettings = { trim: "6x9", bleed: true, fonts: DEFAULT_FONTS };
 
 export function normalizeBook(book: Book): Book {
   const chapters = (Array.isArray(book.chapters) ? book.chapters : []).filter(Boolean);
   return {
     ...book,
     metadata: { ...DEFAULT_METADATA, ...book.metadata },
-    settings: { ...DEFAULT_SETTINGS, ...book.settings },
+    settings: { ...DEFAULT_SETTINGS, ...book.settings, fonts: { ...DEFAULT_FONTS, ...book.settings?.fonts } },
     cover: book.cover ? { ...createCover(), ...book.cover } : createCover(),
     chapters: (chapters.length ? chapters : [createChapter()]).map((c) =>
       c.updatedAt ? c : { ...c, updatedAt: Date.now() },

src/model/fonts.ts

@@ -0,0 +1,98 @@
+export type FontCategory = "serif" | "sans" | "display";
+
+export interface BundledFont {
+  id: string;
+  label: string;
+  family: string;
+  category: FontCategory;
+  regular: string;
+  italic?: string;
+  weight: string;
+}
+
+export const BUNDLED_FONTS: BundledFont[] = [
+  { id: "literata", label: "Literata", family: "Literata", category: "serif", regular: "Literata-VF.ttf", italic: "Literata-Italic-VF.ttf", weight: "200 900" },
+  { id: "eb-garamond", label: "EB Garamond", family: "EB Garamond", category: "serif", regular: "EBGaramond-VF.ttf", italic: "EBGaramond-Italic-VF.ttf", weight: "400 800" },
+  { id: "lora", label: "Lora", family: "Lora", category: "serif", regular: "Lora-VF.ttf", italic: "Lora-Italic-VF.ttf", weight: "400 700" },
+  { id: "source-serif", label: "Source Serif 4", family: "Source Serif 4", category: "serif", regular: "SourceSerif4-VF.ttf", italic: "SourceSerif4-Italic-VF.ttf", weight: "200 900" },
+  { id: "fraunces", label: "Fraunces", family: "Fraunces", category: "display", regular: "Fraunces-VF.ttf", italic: "Fraunces-Italic-VF.ttf", weight: "100 900" },
+  { id: "hanken", label: "Hanken Grotesk", family: "Hanken Grotesk", category: "sans", regular: "HankenGrotesk-VF.ttf", italic: "HankenGrotesk-Italic-VF.ttf", weight: "100 900" },
+];
+
+export type FontRef =
+  | { kind: "bundled"; id: string }
+  | { kind: "system"; family: string };
+
+export interface BookFonts {
+  body: FontRef;
+  heading: FontRef;
+}
+
+export interface FontPairing {
+  id: string;
+  label: string;
+  body: FontRef;
+  heading: FontRef;
+}
+
+const bundled = (id: string): FontRef => ({ kind: "bundled", id });
+
+export const FONT_PAIRINGS: FontPairing[] = [
+  { id: "quiet-press", label: "Quiet Press", body: bundled("literata"), heading: bundled("literata") },
+  { id: "classic", label: "Classic", body: bundled("eb-garamond"), heading: bundled("eb-garamond") },
+  { id: "editorial", label: "Editorial", body: bundled("source-serif"), heading: bundled("fraunces") },
+  { id: "modern", label: "Modern", body: bundled("lora"), heading: bundled("hanken") },
+  { id: "contrast", label: "Contrast", body: bundled("literata"), heading: bundled("hanken") },
+];
+
+export const DEFAULT_FONTS: BookFonts = { body: bundled("literata"), heading: bundled("literata") };
+
+const SERIF_FALLBACK = `Georgia, "Times New Roman", serif`;
+const SANS_FALLBACK = `ui-sans-serif, system-ui, -apple-system, sans-serif`;
+
+export function bundledFont(id: string): BundledFont | undefined {
+  return BUNDLED_FONTS.find((f) => f.id === id);
+}
+
+export function fontFamilyName(ref: FontRef): string {
+  if (ref.kind === "system") return ref.family;
+  return bundledFont(ref.id)?.family ?? "Literata";
+}
+
+export function fontLabel(ref: FontRef): string {
+  if (ref.kind === "system") return ref.family;
+  return bundledFont(ref.id)?.label ?? ref.id;
+}
+
+export function fontStack(ref: FontRef): string {
+  if (ref.kind === "bundled") {
+    const font = bundledFont(ref.id);
+    if (!font) return SERIF_FALLBACK;
+    return `"${font.family}", ${font.category === "sans" ? SANS_FALLBACK : SERIF_FALLBACK}`;
+  }
+  return `"${ref.family}", ${SERIF_FALLBACK}`;
+}
+
+export function refsEqual(a: FontRef, b: FontRef): boolean {
+  if (a.kind !== b.kind) return false;
+  return a.kind === "bundled" ? a.id === (b as { id: string }).id : a.family === (b as { family: string }).family;
+}
+
+export function pairingFor(fonts: BookFonts): string | null {
+  const match = FONT_PAIRINGS.find((p) => refsEqual(p.body, fonts.body) && refsEqual(p.heading, fonts.heading));
+  return match?.id ?? null;
+}
+
+export function fontsUsed(fonts: BookFonts): { bundled: BundledFont[]; system: string[] } {
+  const usedBundled = new Map<string, BundledFont>();
+  const usedSystem = new Set<string>();
+  for (const ref of [fonts.body, fonts.heading]) {
+    if (ref.kind === "bundled") {
+      const font = bundledFont(ref.id);
+      if (font) usedBundled.set(font.id, font);
+    } else {
+      usedSystem.add(ref.family);
+    }
+  }
+  return { bundled: [...usedBundled.values()], system: [...usedSystem] };
+}