Add option to hide MCP resources from @ file picker autocomplete

Feature Request

When using the @ file picker to reference local files, MCP resources (like Figma files) appear alongside filesystem files in the autocomplete suggestions.

Problem

Users who want to use MCP plugins (e.g., Figma) for their tools but don't want MCP resources cluttering the file picker autocomplete have no way to configure this behavior.

<img width="555" height="160" alt="Image" src="https://github.com/user-attachments/assets/4edece52-0e1a-4a56-bf6b-88dfb3fe6fe0" />

Proposed Solution

Add a setting to control whether MCP resources appear in the @ file picker autocomplete, such as:

{
  "showMcpResourcesInFilePicker": false
}

Or per-plugin configuration:

{
  "enabledPlugins": {
    "figma@claude-plugins-official": {
      "enabled": true,
      "showInFilePicker": false
    }
  }
}

Current Workaround

The only current option is to disable the MCP plugin entirely, which removes access to its tools as well.

Use Case

Users want access to Figma tools (implement design, code connect, etc.) without Figma file resources appearing when trying to reference local project files.