Multi-select plugin installation only installs the last selected plugin

Bug Description

When selecting multiple plugins for installation via /plugin, only the last selected plugin is actually installed.

Steps to Reproduce

1. Run /plugin in Claude Code CLI
2. Select multiple plugins from the list (e.g., plugin A, plugin B, plugin C)
3. Confirm installation
4. Only the last selected plugin (plugin C) gets installed
5. The output shows only one ✓ Installed <last-plugin> message

Expected Behavior

All selected plugins should be installed, not just the last one.

Actual Behavior

Only the last plugin in the selection is installed. The others are silently ignored.

Environment

• OS: macOS (Darwin 25.3.0)
• Claude Code: latest
• Shell: zsh