VS Code extension does not adopt ~/Library/Application Support/Code/User/mcp.json in 1.112.0

## Problem
VS Code extension does not adopt ~/Library/Application Support/Code/User/mcp.json in 1.112.0 2026-03-06

## Steps to reproduce the issue

1. Add MCP to VS Code, for example from [this GitHub MCP link](https://github.com/awslabs/mcp?tab=readme-ov-file#-real-time-access-to-official-aws-documentation)
2. Verify that MCP server is in `mcp.json`
3. MCP server is not listed in `Chat, MCP servers.`
_Note:_ MCP server can be added manually in extension but is a lot of work. Adding manually does not alter `mcp.json`. IOW, the extension ignores `mcp.json` instead of duplicating a manually added entry.

## Expected behavior
Extension should mirror all settings in VS Code user `mcp.json`

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

- OS: macOS 26.4
- Visual Studio Code version: 1.113.0
- AWS Toolkit version: 3.101.0
- Amazon Q version: 1.112.0

Reproduce the issue with the VS Code user mcp.json on macOS using the listed extension and VS Code versions. Trace the extension's MCP configuration discovery and loading entry points; done means servers defined in the user mcp.json appear in Chat's MCP servers without manual duplication.

Written by the indexing model from the issue text.