[UI] MCP marketplace shows 'Install' button for already-installed servers

Description

The MCP marketplace panel in the Claude Code IDE sidebar always shows the "Install" button for every featured server, regardless of whether the user has already installed that server locally via \claude mcp add\.

This makes it visually impossible to tell at a glance which marketplace items are already set up and which are not.

Steps to reproduce

1. Install an MCP server from the featured marketplace list via CLI:

\\\bash
claude mcp add markitdown /path/to/markitdown-mcp
claude mcp add context7 -- npx -y @upstash/context7-mcp
\\\

1. Verify they are connected:

\\\bash
claude mcp list
# markitdown: ... ✓ Connected
# context7: ... ✓ Connected
\\\

1. Open the IDE sidebar → \"MCP Servers\" panel
2. Observe: Markitdown and Context7 still show the blue \"Install\" button as if they were not installed.

Expected behavior

Already-installed servers should either:

• Show \"Installed\" / \"✓\" instead of the Install button, or
• Be visually de-emphasized (greyed out), or
• Offer a \"Configure\" / \"Remove\" action instead of \"Install\"

Actual behavior

The marketplace UI is purely a static featured list and never reflects the local \claude mcp list\ state. Clicking \"Install\" on something already installed produces a duplicate-name error.

Environment

• Claude Code version: 2.1.132
• OS: macOS 26.4.1 (Tahoe, ARM)
• MCP servers configured locally: filesystem, firecrawl, markitdown, context7