Implement multi-session support and welcome screen in EditorManager

- Removed the homepage display logic and replaced it with a welcome screen that appears when no ROM is loaded or no active editors are present.
- Enhanced session management by iterating through all sessions to check for active editors, allowing for better multi-session docking.
- Introduced new methods for generating unique editor titles based on session context and added feature flags for per-session configurations.
- Added safeguards for ROM loading state checks in editor methods to prevent operations on unloaded ROMs.

src/app/editor/editor_safeguards.h

@@ -0,0 +1,42 @@
+#ifndef YAZE_APP_EDITOR_SAFEGUARDS_H
+#define YAZE_APP_EDITOR_SAFEGUARDS_H
+
+#include "absl/status/status.h"
+#include "absl/strings/str_format.h"
+
+namespace yaze {
+namespace editor {
+
+// Macro for checking ROM loading state in editor methods
+#define REQUIRE_ROM_LOADED(rom_ptr, operation) \
+  do { \
+    if (!(rom_ptr) || !(rom_ptr)->is_loaded()) { \
+      return absl::FailedPreconditionError( \
+          absl::StrFormat("%s: ROM not loaded", (operation))); \
+    } \
+  } while (0)
+
+// Macro for ROM state checking with custom error message
+#define CHECK_ROM_STATE(rom_ptr, message) \
+  do { \
+    if (!(rom_ptr) || !(rom_ptr)->is_loaded()) { \
+      return absl::FailedPreconditionError(message); \
+    } \
+  } while (0)
+
+// Helper function for generating consistent ROM status messages
+inline std::string GetRomStatusMessage(const Rom* rom) {
+  if (!rom) return "No ROM loaded";
+  if (!rom->is_loaded()) return "ROM failed to load";
+  return absl::StrFormat("ROM loaded: %s", rom->title());
+}
+
+// Helper function to check if ROM is in a valid state for editing
+inline bool IsRomReadyForEditing(const Rom* rom) {
+  return rom && rom->is_loaded() && !rom->title().empty();
+}
+
+}  // namespace editor
+}  // namespace yaze
+
+#endif  // YAZE_APP_EDITOR_SAFEGUARDS_H