fix: duplicate filament sets, meshes and segmentations (v2.0)

[uermel]

Port of the main-line fix to v2.0 (plus the test stub for copick_object_type).

The duplicate (📋) button on the object tables did nothing for:

• filament sets: duplicateClicked was never connected and there was no handler;
• meshes and segmentations: the handlers were # TODO stubs.

Change

• A shared _duplicate_entity stores pending edits first, so the copy includes them, then copies the entry to the user / session chosen in the Duplicate dialog. It uses copick's copy_copick_objects.
• A segmentation keeps its type (binary, multilabel, instance or panoptic) and voxel size.
• The table is refreshed, and the copy is shown and marked active.
• If the target already exists, a warning names it.
• update_meshes_table() is added, mirroring the segmentations one.

Tested in ChimeraX 1.12 on a copy of the 10521 test project:

• filament set: copied with all filaments, listed and shown;
• a second copy to the same session is refused with a warning;
• instance segmentation: copied, keeps its type and voxel size;
• mesh: copied.

Unit tests and the CI lint steps pass on both lines.

🤖 Generated with Claude Code