feat(cli): add status field to thread show output

- Add ThreadStatus type to workflow-protocol
- Update StepOutput type to include status field alongside deprecated done/background fields
- Implement status computation in cmdThreadShow (idle/running/completed/cancelled)
- Update cmdThreadStepOnce to include status in return values
- Add comprehensive test suite for thread show status scenarios

Fixes #559

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/cli-workflow/src/cli.ts

@@ -1,6 +1,6 @@
 #!/usr/bin/env node
 
-import type { CasRef, ThreadId } from "@uncaged/workflow-protocol";
+import type { CasRef, ThreadId, ThreadStatus } from "@uncaged/workflow-protocol";
 import { Command } from "commander";
 import {
   cmdCasGet,
@@ -38,7 +38,6 @@ import {
   cmdThreadStart,
   cmdThreadStop,
   THREAD_READ_DEFAULT_QUOTA,
-  type ThreadStatus,
 } from "./commands/thread.js";
 import { parseTimeInput } from "./commands/thread-time-parser.js";
 import { cmdWorkflowAdd, cmdWorkflowList, cmdWorkflowShow } from "./commands/workflow.js";