Plugins installed but not added to enabledPlugins - don't appear in Installed tab

Bug Description

When installing plugins via /plugin, they are tracked in installed_plugins.json but NOT added to enabledPlugins in settings.json. This causes:

1. Plugins show as "installed" (with checkmark) in the Marketplace tab
2. But they don't appear in the "Installed" tab
3. Clicking on an "installed" plugin in Marketplace redirects to Discover tab instead of allowing reinstall/uninstall

Steps to Reproduce

1. Run /plugin and install a plugin (e.g., supabase)
2. Restart Claude Code as prompted
3. Run /plugin again
4. Go to "Installed" tab - plugin is NOT listed
5. Go to "Marketplace" tab - plugin shows with checkmark indicating installed
6. Click on the plugin - redirects to Discover tab instead of showing plugin details

Expected Behavior

• Installed plugins should appear in the "Installed" tab
• Installing a plugin should add it to both installed_plugins.json AND settings.json enabledPlugins

Actual Behavior

• Plugins are added to ~/.claude/plugins/installed_plugins.json ✓
• Plugins are NOT added to ~/.claude/settings.json enabledPlugins ✗
• Installed tab only shows plugins that are in enabledPlugins

Workaround

Manually edit ~/.claude/settings.json and add all plugins from installed_plugins.json to the enabledPlugins object:

{
  "enabledPlugins": {
    "plugin-name@marketplace": true
  }
}

Environment

• OS: Windows 11
• Claude Code version: Latest (Jan 2026)