/mcp dialog doesn't show MCP servers added via `claude mcp add`

Bug

MCP servers added via claude mcp add (stored in .claude.json under projects.<path>.mcpServers) do not appear in the /mcp interactive dialog. Only plugin-managed MCP servers (e.g., context7, playwright) are listed there.

Steps to reproduce

1. Add an MCP server via CLI: claude mcp add github -- npx -y @modelcontextprotocol/server-github
2. Confirm it's working — tools are available and functional in the session
3. Open /mcp — the server does not appear in the list

Expected behavior

All active MCP servers should appear in the /mcp dialog, regardless of whether they were added via a plugin or via claude mcp add.

Actual behavior

/mcp only shows plugin-managed servers. The standalone server works fine (tools load, calls succeed), but there's no way to see its status, reconnect, or manage it from the /mcp UI.

Workaround

claude mcp list in the terminal shows the server correctly.

Environment

• Claude Code CLI (native install, macOS Darwin 25.3.0)