fix(cli): improve usage output format + fix skill index title

- Usage: grouped sections with titles, aligned descriptions
- Header: 'uncaged-workflow — workflow engine CLI'
- Footer: 'Use <command> --help for subcommand details.'
- Fix skill index title: 'uncaged-workflow skill' (was: help --skill)
- 242 tests pass

Closes #85

小橘 🍊

packages/cli-workflow/__tests__/help.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, test } from "bun:test";
-import { runCli } from "../src/cli-dispatch.js";
+import { formatCliUsage, runCli } from "../src/cli-dispatch.js";
 import {
   formatSkillDoc,
   formatSkillIndex,
@@ -90,6 +90,8 @@ describe("getSkillTopics", () => {
 describe("formatSkillIndex", () => {
   test("lists all topics", () => {
     const idx = formatSkillIndex();
+    expect(idx).toContain("# uncaged-workflow skill");
+    expect(idx).not.toContain("# uncaged-workflow help --skill");
     expect(idx).toContain("cli");
     expect(idx).toContain("develop");
     expect(idx).toContain("author");
@@ -97,6 +99,35 @@ describe("formatSkillIndex", () => {
   });
 });
 
+describe("formatCliUsage", () => {
+  test("has tagline, grouped sections, help hint, and env vars", () => {
+    const u = formatCliUsage();
+    expect(u.startsWith("uncaged-workflow — workflow engine CLI")).toBe(true);
+    expect(u).toContain("Workflow registry:");
+    expect(u).toContain("Thread execution:");
+    expect(u).toContain("Content-addressable storage:");
+    expect(u).toContain("Development:");
+    expect(u).toContain("Shortcuts:");
+    expect(u).toContain("Reference:");
+    expect(u).toContain("skill [topic]");
+    expect(u).toContain("Agent-consumable docs");
+    expect(u).toContain("Use <command> --help for subcommand details.");
+    expect(u).toContain("Environment variables:");
+    expect(u).toContain("WORKFLOW_STORAGE_ROOT");
+    expect(u).toContain("UNCAGED_WORKFLOW_STORAGE_ROOT");
+  });
+
+  test("lists commands from registry with descriptions", () => {
+    const u = formatCliUsage();
+    expect(u).toContain("workflow add");
+    expect(u).toContain("Register a workflow bundle in the registry");
+    expect(u).toContain("thread run");
+    expect(u).toContain("Start a new thread executing a workflow");
+    expect(u).toContain("cas gc");
+    expect(u).toContain("Garbage-collect unreferenced CAS entries");
+  });
+});
+
 describe("formatSkillTopic('cli') — legacy formatSkillDoc", () => {
   const doc = formatSkillDoc();
 

packages/cli-workflow/__tests__/init-workspace.test.ts

@@ -129,8 +129,9 @@ describe("init workspace", () => {
 
   test("usage lists init subcommands", () => {
     const u = formatCliUsage();
-    expect(u).toContain("uncaged-workflow init workspace <name>");
-    expect(u).toContain("uncaged-workflow init template <name>");
+    expect(u).toContain("init workspace <name>");
+    expect(u).toContain("init template <name>");
+    expect(u).toContain("Development:");
   });
 
   test("runCli rejects unknown init subcommand", async () => {