Plugin marketplace UI shows incorrect installation count after marketplace updates

Bug Description

When a plugin marketplace repository adds new plugins after initial installation, the /plugins command and plugin management UI show inconsistent plugin counts.

Steps to Reproduce

1. Install a plugin marketplace from a GitHub repository using /plugins
2. Marketplace initially has N plugins (e.g., 4 plugins)
3. Later, a new plugin is added to the marketplace repository (now N+1 plugins)
4. Remove and re-add the marketplace using /plugins
5. Run /plugins - shows the marketplace has N+1 plugins installed
6. Go to manage plugins - shows only N plugins installed

Expected Behavior

After removing and re-adding a marketplace, both the /plugins list view and the management UI should show the same number of plugins (N+1).

Actual Behavior

• /plugins list view: Shows N+1 plugins (reads from filesystem)
• Plugin management UI: Shows N plugins (reads from installed_plugins.json)

Technical Details

The issue appears to be in how Claude Code handles marketplace updates:

1. ~/.claude/plugins/installed_plugins.json contains:

• Stale git commit SHA from initial installation
• Only lists original N plugins

1. Filesystem at ~/.claude/plugins/marketplaces/[name]/plugins/ contains:

• Latest git commit with N+1 plugins
• All plugin directories present with proper .claude-plugin/plugin.json files

1. When removing and re-adding the marketplace:

• ✅ Git repository is updated to latest commit
• ❌ installed_plugins.json is NOT updated with new plugins
• ❌ Git commit SHA in installed_plugins.json remains stale

Impact

• Users cannot enable/disable newly added plugins via the management UI
• Plugins may work via /plugins list but appear missing in management
• Inconsistent UX between different plugin interfaces

Environment

• Claude Code public beta
• Using GitHub-hosted plugin marketplace

Suggested Fix

When syncing/updating a marketplace, Claude Code should:

1. Re-scan the plugins directory
2. Update installed_plugins.json with any new plugins found
3. Update the git commit SHA reference for each plugin