Add README.md upload to dataset repo for HF viewer image column rendering

The HF viewer needs YAML frontmatter in README.md to identify image columns.
Generated from hf_meta so the schema stays in one place. Uploaded once on
first inference (skipped if README.md already exists).

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

app.py

@@ -187,6 +187,22 @@ def update_dimensions_on_upload(image):
     return (nw // 8) * 8, (nh // 8) * 8
 
 
+def _readme_from_features(feats):
+    lines = ["---", "configs:", "- config_name: default",
+             "  data_files:", "  - split: train",
+             "    path: data/*.parquet", "  features:"]
+    for name, f in feats.items():
+        lines.append(f"  - name: {name}")
+        if f.get("_type") == "Image":
+            lines.append("    dtype: image")
+        elif f.get("_type") == "Sequence" and f.get("feature", {}).get("_type") == "Image":
+            lines.append("    sequence: image")
+        else:
+            lines.append(f"    dtype: {f.get('dtype', 'string')}")
+    lines.append("---")
+    return "\n".join(lines) + "\n"
+
+
 def log_inference(pil_inputs, output_pil, prompt, seed, steps, guidance_scale,
                   input_width, input_height, duration_seconds, success, error_message=""):
     if not HF_TOKEN or not DATASET_REPO:
@@ -267,6 +283,16 @@ def log_inference(pil_inputs, output_pil, prompt, seed, steps, guidance_scale,
         api = HfApi(token=HF_TOKEN)
         api.create_repo(repo_id=DATASET_REPO, repo_type="dataset", private=True, exist_ok=True)
 
+        # Upload README.md once so the HF viewer knows the column types.
+        try:
+            hf_hub_download(repo_id=DATASET_REPO, filename="README.md",
+                            repo_type="dataset", token=HF_TOKEN)
+        except Exception:
+            readme = _readme_from_features(_json.loads(hf_meta)["info"]["features"])
+            api.upload_file(path_or_fileobj=readme.encode(), path_in_repo="README.md",
+                            repo_id=DATASET_REPO, repo_type="dataset")
+            print("[log] uploaded README.md with feature schema")
+
         try:
             local_path = hf_hub_download(
                 repo_id=DATASET_REPO, filename=path_in_repo,