fix: resolve YAML syntax error in create-release-tag workflow (#429)

Replace heredoc with echo statements to fix YAML parsing issue. The
unindented heredoc content was breaking out of the literal block scalar,
causing `---` to be interpreted as a YAML document separator.

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

Co-authored-by: Claude <noreply@anthropic.com>

.github/workflows/create-release-tag.yml

@@ -53,16 +53,16 @@ jobs:
         ' CHANGELOG.md > release_notes.md
 
         # Append install instructions
-        cat >> release_notes.md << 'EOF'
-
----
-
-**PyPI:** https://pypi.org/project/claude-agent-sdk/VERSION/
-
-```bash
-pip install claude-agent-sdk==VERSION
-```
-EOF
+        {
+          echo ""
+          echo "---"
+          echo ""
+          echo "**PyPI:** https://pypi.org/project/claude-agent-sdk/VERSION/"
+          echo ""
+          echo '```bash'
+          echo "pip install claude-agent-sdk==VERSION"
+          echo '```'
+        } >> release_notes.md
 
         # Replace VERSION placeholder
         sed -i "s/VERSION/$VERSION/g" release_notes.md