feat(editor): implement multi-pane split layout

src/cm/commandRegistry.js

@@ -213,6 +213,56 @@ function registerCoreCommands() {
 			return true;
 		},
 	});
+	addCommand({
+		name: "newPane",
+		description: "Create new editor pane",
+		readOnly: true,
+		requiresView: false,
+		run() {
+			acode.exec("new-pane");
+			return true;
+		},
+	});
+	addCommand({
+		name: "moveTabToNewPane",
+		description: "Move current tab to new pane",
+		readOnly: true,
+		requiresView: false,
+		run() {
+			acode.exec("move-tab-to-new-pane");
+			return true;
+		},
+	});
+	addCommand({
+		name: "closePane",
+		description: "Close active editor pane",
+		readOnly: true,
+		requiresView: false,
+		run() {
+			acode.exec("close-pane");
+			return true;
+		},
+	});
+	addCommand({
+		name: "focusNextPane",
+		description: "Focus next editor pane",
+		readOnly: true,
+		requiresView: false,
+		run() {
+			acode.exec("focus-next-pane");
+			return true;
+		},
+	});
+	addCommand({
+		name: "focusPreviousPane",
+		description: "Focus previous editor pane",
+		readOnly: true,
+		requiresView: false,
+		run() {
+			acode.exec("focus-previous-pane");
+			return true;
+		},
+	});
 	addCommand({
 		name: "closeAllTabs",
 		description: "Close all tabs",

src/cm/editorUtils.ts

@@ -22,6 +22,24 @@ export interface ScrollPosition {
 	scrollLeft: number;
 }
 
+const docTextCache = new WeakMap<object, string>();
+
+/**
+ * CodeMirror Text documents are immutable, so the full string can be cached
+ * per document object and reused across compatibility/plugin reads.
+ */
+export function getDocText(
+	doc: { toString(): string } | string | null | undefined,
+): string {
+	if (!doc) return "";
+	if (typeof doc !== "object" && typeof doc !== "function") return String(doc);
+	const cached = docTextCache.get(doc);
+	if (cached !== undefined) return cached;
+	const text = doc.toString();
+	docTextCache.set(doc, text);
+	return text;
+}
+
 /**
  * Get all folded ranges from CodeMirror editor state
  */

src/cm/lsp/references.ts

@@ -5,6 +5,7 @@ import {
 	openReferencesTab,
 	showReferencesPanel,
 } from "components/referencesPanel";
+import { getDocText } from "cm/editorUtils";
 import settings from "lib/settings";
 
 interface Position {
@@ -61,7 +62,7 @@ async function fetchLineText(uri: string, line: number): Promise<string> {
 				}
 			}
 			if (typeof doc.toString === "function") {
-				const content = doc.toString();
+				const content = getDocText(doc as { toString(): string });
 				const lines = content.split("\n");
 				if (lines[line] !== undefined) {
 					return lines[line];

src/components/sidebar/index.js

@@ -644,7 +644,12 @@ function create($container, $toggler) {
 		root.style.width = `calc(100% - ${width}px)`;
 		clearTimeout(setWidthTimeout);
 		setWidthTimeout = setTimeout(() => {
-			editorManager?.editor?.resize(true);
+			const editor = editorManager?.editor;
+			if (typeof editor?.resize === "function") {
+				editor.resize(true);
+			} else {
+				editor?.requestMeasure?.();
+			}
 		}, 300);
 	}