feat: Add ebook view modes with Feature Registration Pattern

Convert view-modes.ts to init(context) pattern with:
- Paginated mode with pagination controls
- Scrolled mode for continuous reading
- Single and double column layouts
- Event-based navigation and mode switching

web/src/reader/ebook/view-modes.ts

@@ -1,4 +1,38 @@
 // Different viewing modes for ebooks
+// Feature Registration Pattern implementation
+
+import type { ReaderContext } from "../core/reader-context";
+
+export function init(context: ReaderContext): void {
+  let state: ViewModeState | null = null;
+
+  context.events.on("reader:loaded", (detail: { container: HTMLElement }) => {
+    state = { currentMode: "paginated", currentPage: 1 };
+    setViewMode(detail.container, "paginated");
+  });
+
+  context.events.on("view-mode:set", (detail: { mode: ViewMode }) => {
+    if (state && context.elements.readerContent) {
+      state.currentMode = detail.mode;
+      setViewMode(context.elements.readerContent, detail.mode);
+      context.events.emit("view-mode:changed", { mode: detail.mode });
+    }
+  });
+
+  context.events.on("view-mode:get", () => {
+    if (state) {
+      context.events.emit("view-mode:current", state);
+    }
+  });
+
+  context.events.on("pagination:go-to-page", (detail: { page: number }) => {
+    if (state && context.elements.readerContent) {
+      state.currentPage = detail.page;
+      goToPage(context.elements.readerContent, detail.page);
+      context.events.emit("pagination:page-changed", { page: detail.page });
+    }
+  });
+}
 
 type ViewMode = "paginated" | "scrolled" | "single-column" | "double-column";
 
@@ -11,7 +45,9 @@ function setViewMode(container: HTMLElement, mode: ViewMode): void {
   const content = container.querySelector(".ebook-content");
   if (!content) return;
 
-  content.classList.remove(
+  const element = content as HTMLElement;
+
+  element.classList.remove(
     "paginated",
     "scrolled",
     "single-column",
@@ -20,16 +56,16 @@ function setViewMode(container: HTMLElement, mode: ViewMode): void {
 
   switch (mode) {
     case "paginated":
-      applyPaginatedMode(container, content as HTMLElement);
+      applyPaginatedMode(container, element);
       break;
     case "scrolled":
-      applyScrolledMode(container, content as HTMLElement);
+      applyScrolledMode(container, element);
       break;
     case "single-column":
-      applySingleColumn(content as HTMLElement);
+      applySingleColumn(element);
       break;
     case "double-column":
-      applyDoubleColumn(content as HTMLElement);
+      applyDoubleColumn(element);
       break;
   }
 }
@@ -93,7 +129,7 @@ function disablePagination(container: HTMLElement): void {
 function addPaginationControls(
   container: HTMLElement,
   pageCount: number,
-): ViewModeState {
+): void {
   let currentPage = 1;
 
   const controls = document.createElement("div");
@@ -120,8 +156,6 @@ function addPaginationControls(
   });
 
   container.appendChild(controls);
-
-  return { currentMode: "paginated", currentPage };
 }
 
 function goToPage(container: HTMLElement, pageNumber: number): void {
@@ -152,4 +186,14 @@ function getTotalPageCount(container: HTMLElement): number {
   return Math.ceil(totalHeight / pageHeight);
 }
 
-export { setViewMode, getCurrentViewMode };
+export function getCurrentViewMode(container: HTMLElement): ViewMode {
+  const content = container.querySelector(".ebook-content") as HTMLElement;
+  if (!content) return "paginated";
+
+  if (content.classList.contains("paginated")) return "paginated";
+  if (content.classList.contains("scrolled")) return "scrolled";
+  if (content.classList.contains("single-column")) return "single-column";
+  if (content.classList.contains("double-column")) return "double-column";
+
+  return "paginated";
+}