chore: ignore auto-generated c-track model.sdf

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: MDEAGEWT

.gitignore

@@ -9,3 +9,6 @@ vils.stl
 
 # Auto-generated by generate_compose.py
 docker-compose.override.yml
+
+# Auto-generated from Jinja2 templates at launch time
+src/realgazebo/models/c-track/model.sdf