feat(preprocessing): add binary closing and hole filling option

[404Simon]

No description provided.

[Copilot]

Pull request overview

Adds optional morphological preprocessing steps to the vessel-analysis pipeline to improve skeletonization robustness, and exposes these new controls through the configuration model and the napari UI.

Changes:

• Add optional binary closing and hole-filling steps (with a max hole-size threshold) before thinning, and surface the preprocessed binary in AnalysisResult.
• Extend ExtractionConfig serialization/deserialization to include the new preprocessing settings.
• Add napari widget controls to configure preprocessing and optionally display the preprocessed binary as an extra labels layer.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
vesskel/pipeline.py	Implements optional morphological preprocessing and returns preprocessed_binary in the analysis result.
vesskel/config.py	Adds new extraction settings (closing/fill holes/max hole size/show preprocessed) to the config model + (de)serialization.
vesskel/_napari.py	Exposes new preprocessing options in the napari GUI and conditionally displays the preprocessed binary layer.

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