feat: add chart extraction models

[PeterStaar-IBM]

Summary

• Add a new chart extraction enrichment model powered by https://huggingface.co/ibm-granite/granite-vision-3.3-2b-chart2csv-preview that converts bar, pie, and line charts into structured tabular (CSV) data
• Expose chart extraction via a new --enrich-chart-extraction CLI flag and do_chart_extraction pipeline option
• Fix a type-check bug in DocumentPictureClassifier where item.meta was accessed without verifying it was a PictureMeta instance

Details

The new ChartExtractionModelGraniteVision enrichment model:

• Runs after picture classification and processes pictures classified as bar_chart, pie_chart, or line_chart
• Uses the Granite Vision model to generate CSV output from chart images, then parses it into TableData stored in PictureMeta.tabular_chart
• Supports batched inference with left-padded inputs
• Automatically enables picture classification when chart extraction is turned on, since classification results are needed to identify chart types

Test plan

• Run conversion with --enrich-chart-extraction on documents containing bar, pie, and line charts
• Verify that tabular_chart metadata is populated on chart PictureItems
• Verify non-chart pictures are unaffected
• Confirm the picture classifier type-check fix doesn't regress existing classification behavior

Examples

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gets transformed to,

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[codecov]

Codecov Report

❌ Patch coverage is 28.46715% with 98 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...g/models/stages/chart_extraction/granite_vision.py	26.51%	97 Missing ⚠️
docling/pipeline/base_pipeline.py	66.66%	1 Missing ⚠️

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Related Documentation

Checked 10 published document(s) in 1 knowledge base(s). No updates required.

^{How did I do? Any feedback?}  

[dolfim-ibm]

All good here, we only have to cleanup now.

[Ryzhtus]

Hi! Is there any help needed? I like this feature and believe it could significantly improve my project's data processing pipeline

[dolfim-ibm]

lgtm