Plugin commands not available in background sessions

Summary

Plugin commands (e.g. /pr-review-toolkit:review-pr) are not available in background sessions launched via the CLI. The slash command doesn't appear in autocomplete and cannot be invoked.

Steps to reproduce

1. Start a background Claude Code session (e.g. via the jobs/background session feature)
2. Try to type /pr-review-toolkit:review-pr or any other plugin command
3. Command does not appear in autocomplete and fails to invoke

Expected behavior

Plugin commands installed at user scope should be available in background sessions, same as foreground interactive sessions. The plugins are installed and the command files exist on disk — the session just doesn't load them.

Actual behavior

Command not found / doesn't appear in autocomplete. User has to open a separate foreground session to use plugin commands, which breaks the workflow of doing code review on a PR that was just created in a background session.

Context

• Plugin: pr-review-toolkit@claude-plugins-official
• Command: review-pr
• Plugin is installed at project scope under /Users/chrismcconnell
• Command file exists at ~/.claude/plugins/cache/claude-plugins-official/pr-review-toolkit/unknown/commands/review-pr.md
• Workaround: open a fresh foreground claude session in the repo directory

Suggested fix

Load plugin commands in background sessions the same way they're loaded in foreground sessions. At minimum, document that background sessions don't support plugin commands so users aren't surprised.