feat: F4.6f3 the file explorer and the image viewer

Oracle FileExplorerWindowRun uses Java's explorer and viewer windows as a
person does (the right-click menu, Java's questions answered, the import
window, the viewer's open). Both windows work on the document's files
through the core's operations: the tree of folders and files, the chosen
folder's entries, Java's menu (also as buttons, no right click needed),
copy that stays and cut that goes once pasted, the import; the viewer's
picture and title. Not taken from Java: a file chosen in the tree taken
for a folder, pictures laid over each other, a text file as an empty
picture. writeFiles numbers the entries in the file system's order again
when a rename made a new key.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/editor/src/desktop/desktop.css

@@ -905,3 +905,124 @@
 .file-dialog-entries button[aria-pressed='true'] {
   background: #b8cfe5;
 }
+
+/* The file explorer (GUIApplicationFileExplorerWindow): the menu's actions
+ * as buttons, the tree beside the folder's entries (one above the other on
+ * a narrow screen). */
+.file-explorer {
+  position: relative;
+  flex: 1;
+  min-height: 0;
+  display: flex;
+  flex-direction: column;
+  gap: 5px;
+  padding: 5px;
+  background: #eeeeee;
+}
+
+.file-explorer-bar {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 5px;
+  flex: none;
+}
+
+.file-explorer-bar button {
+  min-width: 44px;
+  min-height: 40px;
+  padding: 0 10px;
+  border: 1px solid #a0a0a0;
+  border-radius: 6px;
+  background: #f8f8f8;
+  color: #000000;
+  font: 13px Dialog, sans-serif;
+  cursor: pointer;
+}
+
+.file-explorer-bar button:disabled {
+  color: #a0a0a0;
+  cursor: default;
+}
+
+.file-explorer-body {
+  flex: 1;
+  min-height: 0;
+  display: flex;
+  gap: 5px;
+}
+
+.file-explorer-tree,
+.file-explorer-entries {
+  flex: 1;
+  min-width: 0;
+  margin: 0;
+  padding: 0;
+  overflow: auto;
+  border: 1px solid #a0a0a0;
+  background: #ffffff;
+  list-style: none;
+}
+
+.file-explorer-tree button,
+.file-explorer-entries button {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  width: 100%;
+  min-height: 32px;
+  padding: 0 6px;
+  border: 0;
+  background: transparent;
+  color: #000000;
+  font: 13px Dialog, sans-serif;
+  text-align: left;
+  cursor: pointer;
+}
+
+.file-explorer-tree button[aria-current='true'],
+.file-explorer-tree button[aria-pressed='true'],
+.file-explorer-entries button[aria-pressed='true'] {
+  background: #b8cfe5;
+}
+
+@media (max-width: 639px) {
+  .file-explorer-body {
+    flex-direction: column;
+  }
+}
+
+.file-import label button {
+  flex: none;
+}
+
+.file-import-output {
+  min-height: 1.5em;
+  margin: 0;
+  font-weight: bold;
+  white-space: pre-line;
+}
+
+/* The image viewer (GUIApplicationImageViewerWindow): "Öffnen" above, the picture below. */
+.image-viewer {
+  position: relative;
+  flex: 1;
+  min-height: 0;
+  display: flex;
+  flex-direction: column;
+  gap: 5px;
+  padding: 5px;
+  background: #eeeeee;
+}
+
+.image-viewer-picture {
+  flex: 1;
+  min-height: 0;
+  overflow: auto;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.image-viewer-picture img {
+  max-width: 100%;
+}