chore: ignore Runtime local artifacts

[hyeokjun32]

Summary

• Added ignore rules for local Runtime build/output artifacts.
• Prevented build-ort/ and local example model files from being accidentally committed.

Validation

• bash scripts/smoke_default.sh
• python3 tests/test_manifest_compare_identity.py, if run
• git status --short

Notes

• No runtime behavior changed.
• Existing local untracked files were not deleted.