remove compose file names, update docker model runner syntax

[jordanstephens]

Summary

• Updates mastra-extended compose files to use the modern Docker Compose model runner syntax
• Removes hardcoded name: fields from compose files across 80+ samples (cleanup)
• Removes the check in check-sample-files.sh that required compose files to have names

Test plan

• Verify mastra-extended sample builds and deploys correctly with updated compose files
• Confirm other samples still validate correctly without top-level name: fields

🤖 Generated with Claude Code

Samples Checklist

✅ All good!