VS Code extension should inherit MCP servers from ~/.claude.json

Problem

The Claude Code CLI discovers MCP servers configured in ~/.claude.json (user-level config), but the VS Code extension does not. This means MCP servers configured once in the CLI are not available when using Claude Code through the VS Code extension.

The only workaround is to duplicate the MCP config into the project-level .mcp.json, which is problematic when:

• The MCP server uses localhost URLs (machine-specific, should not be committed)
• Multiple projects need the same MCP server (config duplication)
• I expect a single source of truth for my MCP configuration

Expected behavior

The VS Code extension should discover and connect to MCP servers from ~/.claude.json the same way the CLI does, in addition to project-level .mcp.json servers.

Steps to reproduce

1. Configure an MCP server in ~/.claude.json (e.g., via the CLI MCP management UI)
2. Open a project in VS Code with the Claude Code extension
3. The MCP server tools are not available in the extension session
4. The same MCP server works fine in a CLI session in the same directory

Environment

• macOS (Darwin 24.6.0)
• Claude Code VS Code extension