Support a single unified mcp.json for both VS Code and Copilot CLI for maintainability purpose

Description

Currently, VS Code and GitHub Copilot CLI use two different MCP configuration schemas:

• VS Code (.vscode/mcp.json or user-level mcp.json): uses a top-level servers key, and type is optional.
• Copilot CLI (~/.copilot/mcp-config.json, .mcp.json, .github/mcp.json): uses a top-level mcpServers key, and type is required for each server entry.

This forces users who work with both VS Code and Copilot CLI to maintain two near-duplicate JSON files and manually keep them in sync whenever a server is added, removed, or updated — which is error-prone and adds unnecessary maintenance overhead.

Feature Request

Please support a single, unified mcp.json file/schema that can be used by both VS Code and Copilot CLI without conversion. For example:

• Accept the servers key as an alias for mcpServers (or vice versa), and
• Make the type field optional/inferable (e.g. default to stdio/local when command is present, or http when url is present) so existing VS Code configs work as-is.

This would let a single mcp.json (whether at the user/global level or per-repository) be shared across both tools, eliminating duplicate configuration and reducing drift between environments.

Related issues

• #3835 (Incompatible mcp.json schema with VSCode)
• #146 (Respect VS Code User Settings for Copilot CLI Configuration)

比较 .vscode/mcp.json、用户级 mcp.json、~/.copilot/mcp-config.json、.mcp.json 和 .github/mcp.json 中的 schema 和位置。首先跟踪每个配置的发现和验证方式；完成的标准是，同一个 mcp.json 无需手动转换即可在 VS Code 和 Copilot CLI 中都正常工作，包括所请求的键别名和类型处理。