Add Global Bookmark feature

src/activities/home/GlobalBookmarksActivity.h

@@ -0,0 +1,57 @@
+#pragma once
+
+#include <cstddef>
+#include <string>
+#include <vector>
+
+#include "../Activity.h"
+#include "util/ButtonNavigator.h"
+
+struct Rect;
+
+// Home-screen activity that aggregates bookmarks from every indexed book and
+// jumps directly into the chosen book/position on Confirm.
+//
+// Data source: GlobalBookmarkIndex (persisted at /.crosspoint/global_bookmarks.bin).
+// Reconciles against the filesystem on entry (drops entries whose source file
+// has disappeared).
+//
+// The display list is a flat vector of rows, where each row is either a book
+// header separator or a bookmark entry belonging to the preceding header.
+class GlobalBookmarksActivity final : public Activity {
+ public:
+  explicit GlobalBookmarksActivity(GfxRenderer& renderer, MappedInputManager& mappedInput)
+      : Activity("GlobalBookmarks", renderer, mappedInput) {}
+
+  void onEnter() override;
+  void onExit() override;
+  void loop() override;
+  void render(RenderLock&&) override;
+
+ private:
+  struct Row {
+    bool isSeparator = false;
+    size_t bookIndex = 0;      // index into GlobalBookmarkIndex entries
+    size_t bookmarkIndex = 0;  // index within that entry's bookmarks (separator: ignored)
+  };
+
+  ButtonNavigator buttonNavigator;
+  std::vector<Row> rows;
+  int selectorIndex = 0;
+
+  void rebuildRows();
+  std::string getRowTitle(int index) const;
+  bool isSeparatorRow(int index) const;
+  int firstSelectableIndex() const;
+
+  void openSelected();
+  void deleteSelected();
+  void renameSelected();
+
+  // Apply a mutation to the underlying per-book BookmarkStore + global index.
+  // `op` is invoked with the loaded store; it should mutate and return true
+  // when something changed worth persisting. Title/cacheDir/isTxt are taken
+  // from the current index entry.
+  template <typename Op>
+  void mutateBook(size_t bookIndex, Op&& op);
+};