DEVX-48: fix: use heredoc syntax for multi-line $GITHUB_ENV values

src/devx/ci/distribute_files.py

@@ -55,7 +55,12 @@ def _write_github_env(key: str, value: str) -> None:
     if not gh_env:
         raise click.ClickException("GITHUB_ENV environment variable is not set")
     with open(gh_env, "a") as f:  # noqa: PTH123
-        f.write(f"{key}={value}\n")
+        if "\n" in value:
+            # Multi-line values require the heredoc syntax in $GITHUB_ENV.
+            delimiter = "EOF"
+            f.write(f"{key}<<{delimiter}\n{value}\n{delimiter}\n")
+        else:
+            f.write(f"{key}={value}\n")
 
 
 @click.command()