LSP tool not detecting language servers from installed plugins

Description

The built-in LSP tool (added in v2.0.74) does not detect language servers configured via installed plugins, returning "No LSP server available for file type" even when the corresponding LSP plugin is properly installed and enabled.

Steps to Reproduce

1. Install the csharp-lsp plugin:

``
claude plugins install csharp-lsp@claude-plugins-official
``

1. Verify the plugin is enabled in ~/.claude/settings.json:

``json
{
"enabledPlugins": {
"csharp-lsp@claude-plugins-official": true
}
}
``

1. Verify the plugin is installed in ~/.claude/plugins/installed_plugins.json

1. Use the LSP tool on a C# file:

``
LSP operation=documentSymbol filePath=src/SomeFile.cs line=1 character=1
``

1. Result: No LSP server available for file type: .cs

Expected Behavior

The LSP tool should detect the csharp-ls language server configured in the marketplace.json lspServers field:

{
  "name": "csharp-lsp",
  "lspServers": {
    "csharp-ls": {
      "command": "csharp-ls",
      "extensionToLanguage": {
        ".cs": "csharp"
      }
    }
  }
}

Environment

• Claude Code version: 2.0.74+
• OS: macOS (Darwin 25.2.0)
• csharp-ls version: 0.20.0.0 (installed via dotnet tool install --global csharp-ls)

Additional Context

• The csharp-ls binary works correctly when tested directly via stdin/stdout with proper LSP headers
• The language server successfully initializes and returns full capabilities
• The issue also affects other LSP plugins (e.g., typescript-lsp returns the same error)
• The installed plugin directory only contains a README.md file, not the full plugin configuration
• The lspServers configuration exists in the marketplace.json but doesn't appear to be read by the LSP tool