fix(coding-agent): split /clone from /fork UX

closes #2962

packages/coding-agent/test/interactive-mode-clone-command.test.ts

@@ -0,0 +1,77 @@
+import { describe, expect, it, vi } from "vitest";
+import { InteractiveMode } from "../src/modes/interactive/interactive-mode.js";
+
+type CloneCommandContext = {
+	sessionManager: { getLeafId: () => string | null };
+	runtimeHost: {
+		fork: (entryId: string, options?: { position?: "before" | "at" }) => Promise<{ cancelled: boolean }>;
+	};
+	handleRuntimeSessionChange: () => Promise<void>;
+	renderCurrentSessionState: () => void;
+	editor: { setText: (text: string) => void };
+	showStatus: (message: string) => void;
+	showError: (message: string) => void;
+	ui: { requestRender: () => void };
+};
+
+type InteractiveModePrototype = {
+	handleCloneCommand(this: CloneCommandContext): Promise<void>;
+};
+
+const interactiveModePrototype = InteractiveMode.prototype as unknown as InteractiveModePrototype;
+
+describe("InteractiveMode /clone", () => {
+	it("clones the current leaf into a new session", async () => {
+		const fork = vi.fn(async () => ({ cancelled: false }));
+		const handleRuntimeSessionChange = vi.fn(async () => {});
+		const renderCurrentSessionState = vi.fn();
+		const setText = vi.fn();
+		const showStatus = vi.fn();
+		const showError = vi.fn();
+		const requestRender = vi.fn();
+
+		const context: CloneCommandContext = {
+			sessionManager: { getLeafId: () => "leaf-123" },
+			runtimeHost: { fork },
+			handleRuntimeSessionChange,
+			renderCurrentSessionState,
+			editor: { setText },
+			showStatus,
+			showError,
+			ui: { requestRender },
+		};
+
+		await interactiveModePrototype.handleCloneCommand.call(context);
+
+		expect(fork).toHaveBeenCalledWith("leaf-123", { position: "at" });
+		expect(handleRuntimeSessionChange).toHaveBeenCalled();
+		expect(renderCurrentSessionState).toHaveBeenCalled();
+		expect(setText).toHaveBeenCalledWith("");
+		expect(showStatus).toHaveBeenCalledWith("Cloned to new session");
+		expect(showError).not.toHaveBeenCalled();
+		expect(requestRender).not.toHaveBeenCalled();
+	});
+
+	it("shows a status message when there is nothing to clone", async () => {
+		const fork = vi.fn(async () => ({ cancelled: false }));
+		const showStatus = vi.fn();
+		const showError = vi.fn();
+
+		const context: CloneCommandContext = {
+			sessionManager: { getLeafId: () => null },
+			runtimeHost: { fork },
+			handleRuntimeSessionChange: vi.fn(async () => {}),
+			renderCurrentSessionState: vi.fn(),
+			editor: { setText: vi.fn() },
+			showStatus,
+			showError,
+			ui: { requestRender: vi.fn() },
+		};
+
+		await interactiveModePrototype.handleCloneCommand.call(context);
+
+		expect(fork).not.toHaveBeenCalled();
+		expect(showStatus).toHaveBeenCalledWith("Nothing to clone yet");
+		expect(showError).not.toHaveBeenCalled();
+	});
+});