Configurable list columns via header right-click

Native checkable menu on the column headers toggles Size, Modified,
Kind, Rights, Owner and Group (persisted, both panels). Owner/group
come from the ls-style SFTP longname remotely and cached uid/gid
lookups locally (POSIX; undefined on Windows). All columns sort.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/bun/context-menu.ts

@@ -1,4 +1,15 @@
 import { ContextMenu, Utils, type ApplicationMenuItemConfig } from "electrobun/bun";
+import type { ColumnKey } from "../shared/types";
+
+/** Optional list columns, in display order (Name is fixed). */
+const COLUMNS: { key: ColumnKey; label: string }[] = [
+	{ key: "size", label: "Size" },
+	{ key: "mtime", label: "Modified" },
+	{ key: "kind", label: "Kind" },
+	{ key: "rights", label: "Rights" },
+	{ key: "owner", label: "Owner" },
+	{ key: "group", label: "Group" },
+];
 
 export interface RowMenuContext {
 	path: string;
@@ -22,8 +33,14 @@ export class PanelContextMenu {
 	constructor() {
 		ContextMenu.on("context-menu-clicked", (event) => {
 			const action = (event as { data?: { action?: string } }).data?.action;
+			if (!action) return;
+			// column toggles carry no row context
+			if (action.startsWith("col:")) {
+				this.onAction(action);
+				return;
+			}
 			const ctx = this.context;
-			if (!action || !ctx) return;
+			if (!ctx) return;
 			switch (action) {
 				case "ctx-reveal":
 					Utils.showItemInFolder(ctx.path);
@@ -45,6 +62,17 @@ export class PanelContextMenu {
 		ContextMenu.showContextMenu(this.build(context));
 	}
 
+	/** Column picker for the list headers: checkable toggles per column. */
+	showColumns(visible: ColumnKey[]): void {
+		ContextMenu.showContextMenu(
+			COLUMNS.map(({ key, label }) => ({
+				label,
+				action: `col:${key}`,
+				checked: visible.includes(key),
+			})),
+		);
+	}
+
 	private build(ctx: RowMenuContext): ApplicationMenuItemConfig[] {
 		const items: ApplicationMenuItemConfig[] = [];