/plugins Discover hides plugins installed at project scope in other projects

Description

Plugins installed at project scope in one repository are hidden from the Discover section when working in a different repository, even though they're not installed there.

Steps to Reproduce

1. Install a plugin at project scope in Project A:

``
/plugins install frontend-design@claude-plugins-official
# Choose "project" scope
``

1. Open Claude Code in Project B (different repository)

1. Run /plugins and look at the Discover section

1. The plugin installed in Project A does not appear in Discover for Project B

Expected Behavior

Discover should show plugins that are not installed in the current project, regardless of installation status in other projects. Project-scoped plugins are intentionally isolated per-project.

Actual Behavior

Discover filters out any plugin present in ~/.claude/plugins/installed_plugins.json, regardless of scope or projectPath. Once a plugin is installed anywhere, it disappears from Discover everywhere.

Evidence

installed_plugins.json shows the plugin with project scope for a different path:

"frontend-design@claude-plugins-official": [
  {
    "scope": "project",
    "projectPath": "/path/to/project-a",
    ...
  }
]

When in /path/to/project-b, this plugin should appear in Discover but doesn't.

Workaround

Install directly via command:

/plugins install frontend-design@claude-plugins-official

Environment

• Claude Code CLI (latest)
• macOS