feat(cli): add serve command — Hono HTTP API server

Adds `uncaged-workflow serve` command that exposes workflow data
via a local HTTP API for the upcoming Web UI (RFC #118 Phase 1).

Routes:
- GET /healthz — health check
- GET /api/workflows — list registered workflows
- GET /api/workflows/:name — show workflow details
- GET /api/workflows/:name/history — version history
- GET /api/threads — list threads (optional ?workflow= filter)
- GET /api/threads/running — list running threads
- GET /api/threads/:id — show thread records (parsed JSONL)
- GET /api/cas — list CAS hashes
- GET /api/cas/:hash — get CAS content
- POST /api/cas — store content, returns hash
- DELETE /api/cas/:hash — remove CAS entry
- POST /api/cas/gc — garbage collect

Default: 127.0.0.1:7860, configurable via --port/-p and --host.

Refs: #118

packages/cli-workflow/package.json

@@ -7,6 +7,7 @@
   },
   "dependencies": {
     "@uncaged/workflow": "workspace:*",
+    "hono": "^4.12.18",
     "yaml": "^2.8.4"
   },
   "scripts": {