Plugins/CLI: add descriptor-backed lazy root command registration (#57165)

Merged via squash.

Prepared head SHA: ad1dee32eb
Co-authored-by: gumadeiras <5599352+gumadeiras@users.noreply.github.com>
Co-authored-by: gumadeiras <5599352+gumadeiras@users.noreply.github.com>
Reviewed-by: @gumadeiras

src/cli/program/root-help.test.ts

@@ -0,0 +1,46 @@
+import { describe, expect, it, vi } from "vitest";
+
+vi.mock("./core-command-descriptors.js", () => ({
+  getCoreCliCommandDescriptors: () => [
+    {
+      name: "status",
+      description: "Show status",
+      hasSubcommands: false,
+    },
+  ],
+  getCoreCliCommandsWithSubcommands: () => [],
+}));
+
+vi.mock("./subcli-descriptors.js", () => ({
+  getSubCliEntries: () => [
+    {
+      name: "config",
+      description: "Manage config",
+      hasSubcommands: true,
+    },
+  ],
+  getSubCliCommandsWithSubcommands: () => ["config"],
+}));
+
+vi.mock("../../plugins/cli.js", () => ({
+  getPluginCliCommandDescriptors: () => [
+    {
+      name: "matrix",
+      description: "Matrix channel utilities",
+      hasSubcommands: true,
+    },
+  ],
+}));
+
+const { renderRootHelpText } = await import("./root-help.js");
+
+describe("root help", () => {
+  it("includes plugin CLI descriptors alongside core and sub-CLI commands", () => {
+    const text = renderRootHelpText();
+
+    expect(text).toContain("status");
+    expect(text).toContain("config");
+    expect(text).toContain("matrix");
+    expect(text).toContain("Matrix channel utilities");
+  });
+});