dots-mocr: skip whole batch when an image fails to decode

Same class of bug as pp-doclayout's (15cd760) and smoldocling's (8b99222)
fixes from yesterday: the list comprehension
`[dataset[i][image_column] for i in batch_indices]` lives outside the
existing try/except, so one PIL.UnidentifiedImageError takes down the
entire run.

Hit by an overnight 5k BHL run on l4x1 — crashed at batch 150/313 (48%)
after ~10h on a corrupt JP2, no output saved.

Now wrapped in its own try/except. On a corrupt image, the whole batch
is marked `[OCR SKIPPED — UNREADABLE IMAGE]` (length-preserving so the
final add_column still aligns) and the run continues.

Smoke-tested via hf jobs uv run on a 50-image clean slice — confirmed
happy path still works end-to-end (14.2 min, dataset pushed cleanly).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dots-mocr.py

@@ -50,7 +50,7 @@ from typing import Any, Dict, List, Union
 import torch
 from datasets import load_dataset
 from huggingface_hub import DatasetCard, login
-from PIL import Image
+from PIL import Image, UnidentifiedImageError
 from toolz import partition_all
 from tqdm.auto import tqdm
 from vllm import LLM, SamplingParams
@@ -358,7 +358,21 @@ def main(
         desc="dots.mocr processing",
     ):
         batch_indices = list(batch_indices)
-        batch_images = [dataset[i][image_column] for i in batch_indices]
+
+        # Fetch images first, with per-batch fallback for unreadable files.
+        # One corrupt image used to take down the entire run via the list
+        # comprehension; now we mark the whole batch as skipped and continue.
+        try:
+            batch_images = [dataset[i][image_column] for i in batch_indices]
+        except (UnidentifiedImageError, OSError) as e:
+            logger.warning(
+                f"Skipping batch of {len(batch_indices)} — unreadable image "
+                f"in batch: {type(e).__name__}: {e}"
+            )
+            all_outputs.extend(
+                ["[OCR SKIPPED — UNREADABLE IMAGE]"] * len(batch_indices)
+            )
+            continue
 
         try:
             # Create messages for batch