Add automatic segmentation pipeline step

[AssociatedPrimeIdeal]

Goal

Add an optional automatic segmentation step before skeleton and graph generation, with review and correction support.

Tasks

• Add segmentation parameters to the config and CLI.
• Add a pipeline step for automatic segmentation.
• Allow users to enable or disable automatic segmentation and choose the active segmentation source.
• Save generated segmentation outputs and provenance for review and reuse.
• Add GUI support for running segmentation and reviewing/correcting results inside the main workflow.
• Keep popup dialogs limited to segmentation-run configuration if a larger review/edit workspace is added.

Acceptance Criteria

• Existing H5 files with segmentation still work.
• Automatic segmentation can be enabled from config or CLI.
• Generated segmentation is saved to the output directory.
• Users can review and correct generated segmentation without breaking downstream steps.