Incompatible mcp.json schema with VSCode

### Describe the bug

"mcpServers" key in mcp.json incompatible with VSCode "servers" key. requires duplicating mcp server declarations in mcp.json.

also the different locations .github and .vscode require a symlink to point VSCode Copilot Chat and copilot CLI to the same file

### Affected version

_No response_

### Steps to reproduce the behavior

1. create .github/mcp.json with "servers" key
2. symlink from .vscode/mcp.json to .github/mcp.json
3. copilot-cli does not find MCP servers, but VS Code Copilot Chat does.
4. rename "servers" key to "mcpServers"
5. VS Code Copilot Chat does not find the MCP servers anymore, but copilot-cli does.

### Expected behavior

one shared key that is read by both VSCode Copilot Chat and copilot-cli to define mcp servers

### Additional context

current Workaround:

duplicate the "servers" object under "mcpServers" in the same file and symlink it or create two files with the same content except for "servers"/"mcpServers".