[guidelines] workshop/side-quest-12-01-iterate-agent-output.md: raw ✅ Unicode emoji used in Checkpoint heading instead of shortcode

## File reviewed
`workshop/side-quest-12-01-iterate-agent-output.md`

## Violations

### GitHub emoji shortcodes for icons and visual elements
**Offending text:**
> ## ✅ Checkpoint

**Suggested fix:**
Replace the raw Unicode emoji with the GitHub shortcode so the checkpoint heading renders as ``: change the heading to `## :white_check_mark: Checkpoint`.

> Generated by [📋 Guidelines Enforcer](https://github.com/githubnext/gh-aw-workshop/actions/runs/34926567593) · copilot · auto · 142.3 AIC · ⌖ 7.71 AIC · ⊞ 9.5K · [◷](https://github.com/search?q=repo%3Agithubnext%2Fgh-aw-workshop+is%3Aissue+%22gh-aw-workflow-call-id%3A+githubnext%2Fgh-aw-workshop%2Fguidelines-enforcer%22&type=issues)
> - [x] expires on Sep 22, 2026, 4:04 AM UTC

Open workshop/side-quest-12-01-iterate-agent-output.md and find the `## ✅ Checkpoint` heading. Replace the raw Unicode emoji with `:white_check_mark:` as specified, then verify the heading reads `## :white_check_mark: Checkpoint`.

Written by the indexing model from the issue text.