add chart in ResultFormatter

[JaredforReal]

fix #196

[Copilot]

Pull request overview

Fixes #196 by ensuring layout regions labeled as "chart" (typically task_type: "skip") are treated like image regions in ResultFormatter.process(), so they are saved into image_files and embedded into markdown output instead of being silently dropped.

Changes:

• Update ResultFormatter.process() to preserve and render any task_type == "skip" regions (not just label == "image") by carrying an internal _is_image flag through formatting.
• Add a non-empty default label_visualization_mapping in ResultFormatterConfig (including "chart" under the "image" category) to align programmatic defaults with the packaged YAML config.
• Add unit tests covering chart-region inclusion and a fallback case when label_visualization_mapping is explicitly empty.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
glmocr/postprocess/result_formatter.py	Treats task_type: "skip" regions as image regions during filtering + markdown/image resolution.
glmocr/config.py	Sets a default label_visualization_mapping that maps "chart" → "image" (and standardizes other label categories).
glmocr/tests/test_unit.py	Adds regression tests ensuring chart regions produce image_files entries and markdown embeds (including empty-mapping fallback).

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