feat(cli): surface the MCP endpoint in the server-ready banner (#3167)

[os-zhuang]

#3167 的最后一项(可选 DX)。也是这条线最初动机的兑现:#3167 开篇讲的就是 "discoverability is zero exactly where the platform's pitch is strongest — the dev loop"——MCP 端点默认开着、能用、还自我广播(RFC 9728 + /mcp/skill),但 os dev / os serve 的启动输出里没有任何指引,开发者得先知道它在才连得上。

变更

printServerReady 横幅在 MCP 启用时多打一行 URL + SKILL.md 指引:

 ✓ Server is ready
➜ API: http://localhost:3000/
➜ MCP: http://localhost:3000/api/v1/mcp
connect an AI client (Claude Code, Cursor, …) · skill: http://localhost:3000/api/v1/mcp/skill

• 门控在 isMcpServerEnabled()——与自动加载插件、门住路由的同一决策点,所以横幅绝不会广播一个没在服务的端点;OS_MCP_SERVER_ENABLED=false 时不显示。
• 与横幅既有的 API / Console 行同风格,归在端点 URL 组。

验证

运行时验证:开→渲染 URL + skill 行;关→无 MCP 行(见下)。CLI 构建干净、lint 干净、changeset(@objectstack/cli patch)。

=== mcpEnabled: true ===
➜ MCP: http://localhost:3000/api/v1/mcp
connect an AI client (Claude Code, Cursor, …) · skill: http://localhost:3000/api/v1/mcp/skill
=== mcpEnabled: false ===
(无 MCP 行)

合并后 #3167 的四个决策 + 可选 DX 全部完成,建议随之关闭 #3167。

Refs #3167、#3202、#3225。

🤖 Generated with Claude Code

https://claude.ai/code/session_01Pbmw3pMqNJfPbkvwh9Fkjs

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Project	Deployment	Actions	Updated (UTC)
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[github-actions]

📓 Docs Drift Check

This PR changes 1 package(s): @objectstack/cli.

17 hand-written doc(s) reference the affected code and may need an implementation-accuracy re-verification:

• content/docs/ai/skills-reference.mdx(via packages/cli)
• content/docs/api/client-sdk.mdx(via @objectstack/cli)
• content/docs/api/data-flow.mdx(via @objectstack/cli)
• content/docs/api/environment-routing.mdx(via @objectstack/cli)
• content/docs/api/error-catalog.mdx(via @objectstack/cli)
• content/docs/automation/hook-bodies.mdx(via packages/cli)
• content/docs/deployment/backup-restore.mdx(via @objectstack/cli)
• content/docs/deployment/self-hosting.mdx(via @objectstack/cli)
• content/docs/getting-started/cli.mdx(via @objectstack/cli)
• content/docs/getting-started/your-first-project.mdx(via @objectstack/cli)
• content/docs/kernel/runtime-services/data-service.mdx(via packages/cli)
• content/docs/kernel/runtime-services/index.mdx(via packages/cli)
• content/docs/permissions/authentication.mdx(via @objectstack/cli)
• content/docs/plugins/packages.mdx(via @objectstack/cli)
• content/docs/protocol/kernel/plugin-spec.mdx(via @objectstack/cli)
• content/docs/protocol/kernel/realtime-protocol.mdx(via @objectstack/cli)
• content/docs/releases/implementation-status.mdx(via @objectstack/cli)

Advisory only. To re-verify, run the docs-accuracy-audit workflow scoped to these files:
node scripts/docs-audit/affected-docs.mjs origin/main → pass the list as args.docs.