Add reproducible run manifest summarizer

README.md

@@ -64,6 +64,9 @@ versions, SHA-256 fingerprints for every input and exported artifact, and
 normalized dimensions for every input view.
 Downloaded runs can be checked with `python validate_manifest.py
 path/to/*_run.json`; the validator reports missing or tampered artifacts.
+Multiple manifests can be compared with `python summarize_runs.py output`,
+which emits backend, view-count, fusion, coverage, reprojection, fallback, and
+provenance fields as JSON.
 See [TROUBLESHOOTING.md](TROUBLESHOOTING.md) for the scheduler, smoke-test, and
 browser-versus-server failure decision tree.
 Fusion metrics also report the number of distinct dominant source views in the