Plugin not visible in Discover or Installed tabs after local installation in another project

Description

When a plugin is installed locally in one project, it becomes invisible in both the Discover and Installed tabs when trying to access it from a different project. This creates a "ghost state" where the plugin cannot be reinstalled or managed.

Steps to Reproduce

1. Open Claude Code in Project A
2. Install a plugin locally (e.g., frontend-design from marketplace)
3. Exit Claude Code
4. Open Claude Code in Project B
5. Go to /plugin → Discover tab
6. Search for the same plugin (frontend-design)

Expected Behavior

The plugin should be visible in the Discover tab and available for installation in Project B.

Actual Behavior

• Discover tab: Plugin is hidden (treated as "already installed")
• Installed tab: Plugin is not shown (no actual cache files exist for this project)
• Result: Plugin is inaccessible from both tabs

Root Cause (Investigation)

The installed_plugins.json file records the plugin as installed globally, but the actual plugin cache files only exist in the original project's local scope. This metadata/cache mismatch causes the plugin to be filtered out of Discover while not appearing in Installed.

Workaround

Manually remove the plugin entry from installed_plugins.json to make it visible again in the Discover tab.

Environment

• Claude Code version: v2.0.76
• OS: macOS (Darwin 25.2.0)