/mcp dialog doesn't show all configured MCP servers

Description

The /mcp UI dialog only shows claude.ai managed servers and built-in MCPs (plugins). User-scoped MCP servers added via claude mcp add don't appear in the dialog, even though claude mcp list shows them as connected.

Steps to reproduce

1. Add a user-scoped MCP server: claude mcp add paper --transport http http://127.0.0.1:29979/mcp --scope user
2. Verify it's connected: claude mcp list → shows paper: ✓ Connected
3. Run /mcp in a Claude Code session
4. Paper (and other user-scoped servers) are missing from the dialog

Expected behavior

All configured MCP servers should appear in the /mcp dialog, regardless of scope.

Actual behavior

Only claude.ai managed servers and built-in MCPs appear. In my case, 4 user-scoped servers (paper, shadcn-ui, 21st-dev-magic, gemini) are all missing from the UI despite being registered and connected.

Environment

• Claude Code 2.1.91 (native install)
• macOS Darwin 24.6.0