Fix small image filtering in chart extraction stage

[edknv]

Description

This PR fixes the logic for filtering out small images in the chart extraction stage. When we filter out small images, we keep track of the indices in the original image batch in valid_indices and use valid_indices later to restore the original order in the results. The table extraction has similar logic:

nv-ingest/src/nv_ingest/stages/nim/table_extraction.py

Lines 61 to 66 in f4a3819

	if width >= PADDLE_MIN_WIDTH and height >= PADDLE_MIN_HEIGHT:
	valid_images.append(img)
	valid_indices.append(i)
	else:
	# Image is too small; mark as skipped.
	results[i] = (img, (None, None))

nv-ingest/src/nv_ingest/stages/nim/table_extraction.py

Lines 85 to 88 in f4a3819

	# Assign each result back to its original position.
	for idx, result in enumerate(paddle_result):
	original_index = valid_indices[idx]
	results[original_index] = (base64_images[original_index], result)

which we also follow in this PR.

Checklist

• [] I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.