VS Code extension writes global MCP configuration to ~/.aws/amazonq/agents/default.json not mcp.json

## System details (run `AWS: About` and/or `Amazon Q: About`)

- OS: Mac OS
- Visual Studio Code version: 1.103.2
- AWS Toolkit version: 3.71.0
- Amazon Q version: 1.90.0

## Question
According to Docs: https://docs.aws.amazon.com/amazonq/latest/qdeveloper-ug/mcp-ide.html
MCP configuration should be written to ~/.aws/amazonq/mcp.json if an MCP server is configured globally, or .amazonq if local. Instead the configuration is written to agents/default.json. Is this a bug or is documentation oudated?

Start by reproducing the global MCP setup in VS Code with the listed versions, then compare the resulting ~/.aws/amazonq/agents/default.json with the documented ~/.aws/amazonq/mcp.json behavior in the linked MCP IDE guide. Done means determining whether the extension behavior is intentional and ensuring the implementation and documentation agree.

Written by the indexing model from the issue text.