Bug: Removing marketplace does not clean up associated plugin entries in installed_plugins.json

Description

When removing a marketplace via /plugin marketplace remove, the associated plugin entries in ~/.claude/plugins/installed_plugins.json are not cleaned up. This leaves orphaned records that cause persistent "Plugin not found in marketplace" errors.

Steps to Reproduce

1. Install a plugin from a marketplace (e.g., universal-dev-standards from universal-dev-standards marketplace)
2. Later, rename or change the marketplace (e.g., from universal-dev-standards to asia-ostrich)
3. Remove the old marketplace via /plugin marketplace remove universal-dev-standards
4. Claude Code reports "✔ Removed 1 marketplace"
5. However, the plugin entry remains in ~/.claude/plugins/installed_plugins.json:

{
  "plugins": {
    "universal-dev-standards@universal-dev-standards": [
      {
        "scope": "user",
        "installPath": "...",
        "version": "3.3.0-beta.2"
      }
    ]
  }
}

1. Open the plugin management page - see error:

1 error:
  Plugin 'universal-dev-standards' not found in marketplace 'universal-dev-standards'
  → Plugin may not exist in marketplace 'universal-dev-standards'

Expected Behavior

When removing a marketplace, Claude Code should either:

1. Automatically clean up all plugin entries associated with that marketplace from installed_plugins.json
2. Or prompt the user: "This marketplace has X installed plugins. Remove them as well?"

Actual Behavior

• Only the marketplace reference is removed
• Plugin entries in installed_plugins.json become orphaned
• Claude Code continues to validate these orphaned plugins against the non-existent marketplace
• Users see confusing error messages

Workaround

Manually edit ~/.claude/plugins/installed_plugins.json to remove the orphaned plugin entries.

Environment

• OS: macOS (Darwin 24.6.0)
• Claude Code version: Latest (as of 2026-01-09)