Add auto-review step to /work-issue command

Adds step 8 to spawn the code-reviewer agent in background after PR creation.
The agent will review the PR diff and post feedback as a comment.

Closes #11

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

commands/work-issue.md

@@ -12,3 +12,4 @@ argument-hint: <issue-number>
 5. **Commit** with message referencing the issue
 6. **Push**: `git push -u origin <branch>`
 7. **Create PR**: `fj pr create "[Issue #$1] <title>" --body "Closes #$1"`
+8. **Auto-review**: Inform the user that auto-review is starting, then spawn the `code-reviewer` agent in background (using `run_in_background: true`) with the PR number