feat: add ask settings modal shell

tests/ask-settings-command.test.ts

@@ -0,0 +1,58 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import { registerAskSettingsCommand } from "../src/ask-settings-command.ts";
+
+function plainTheme() {
+	return {
+		fg(_color: string, text: string) {
+			return text;
+		},
+		bg(_color: string, text: string) {
+			return text;
+		},
+	};
+}
+
+test("registers /ask-settings and opens the shared modal overlay", async () => {
+	const commands = new Map<
+		string,
+		{ handler: (args: string, ctx: any) => Promise<void> }
+	>();
+	registerAskSettingsCommand({
+		registerCommand(
+			name: string,
+			command: { handler: (args: string, ctx: any) => Promise<void> }
+		) {
+			commands.set(name, command);
+		},
+	} as never);
+
+	assert(commands.has("ask-settings"));
+
+	const customCalls: Array<{ options: unknown; lines: string[] }> = [];
+	await commands.get("ask-settings")?.handler("", {
+		ui: {
+			custom(callback: any, options: unknown) {
+				const done = () => {
+					// test callback intentionally unused
+				};
+				const component = callback(undefined, plainTheme(), undefined, done);
+				customCalls.push({ options, lines: component.render(72) });
+				return Promise.resolve();
+			},
+		},
+	});
+
+	assert.equal(customCalls.length, 1);
+	assert.deepEqual(customCalls[0]?.options, {
+		overlay: true,
+		overlayOptions: {
+			anchor: "center",
+			margin: 1,
+			maxHeight: "90%",
+			minWidth: 26,
+			width: 72,
+		},
+	});
+	assert(customCalls[0]?.lines.join("\n").includes("Keymaps"));
+});