fix: replace raw Unicode ✅ with ✅ shortcode in checkpoint headings (#2665)

Author: github-actions[bot]

workshop/side-quest-25-01-audit-reference.md

@@ -118,7 +118,7 @@ The raw domain-level network access logs live in `sandbox/firewall/audit/` insid
 2. Identify at least one domain the workflow accessed.
 3. If any domains were blocked, add them to `network.allowed` in the workflow frontmatter.
 
-## ✅ Checkpoint
+## :white_check_mark: Checkpoint
 
 - [ ] You can identify each file inside the agent artifact and what it contains
 - [ ] You understand what ⌖ AIC represents and how it differs from agent AIC

workshop/side-quest-26-01-forecast-costs.md

@@ -106,7 +106,7 @@ Recompile after editing:
 gh aw compile
 ```
 
-## ✅ Checkpoint
+## :white_check_mark: Checkpoint
 
 - [ ] You ran `gh aw forecast` and read the P10/P50/P90 output
 - [ ] You used `--period week` to get a shorter projection

workshop/side-quest-enterprise-setup.md

@@ -75,7 +75,7 @@ Agentic workflows require both Actions execution and model access:
 Before installing `gh-aw`, verify with your admin that your account and repository are permitted to run Copilot-powered workflow jobs.
 
 <!-- journey: all -->
-## ✅ Checkpoint
+## :white_check_mark: Checkpoint
 
 - [ ] Your GHES instance is version 3.12 or later (or you are on `github.com`/GHEC)
 - [ ] You know whether Codespaces is available in your enterprise environment