This is helpful for identifying shared steps by name, not index.

This workflow extracts a signed distance function and ocean/land mask from a combined topography dataset on a lat-lon grid.

Supported resolutions are 1/4, 1/8, 1/16 and 1/32 degree.

It supports three different approaches to the land-ocean interface in Antarctica:
1. coastline at the calving front (main supported case for now)
2. coastline at the grounding (future meshes with ice-shelf cavities) ; and
3. coastline at zero bedrock elevation (potential future meshes with wetting-and-drying).

The ocean region is flood-filled from the north pole to ensure that it is contiguous.

It uses critical passages and blockages to ensure that the floodfill includes or excludes the same regions as we want in the final ocean mesh.

Add the unified spherical river workflow used to prepare HydroRIVERS data for mesh generation and analysis.

- add unified-mesh river configuration and shared defaults under polaris.mesh.spherical.unified
- add source, lat-lon, task, step, and visualization plumbing for preparing and inspecting river products
- integrate coastline-aware rasterization and shared HydroRIVERS archiving for the retained network
- add base-mesh river conditioning so downstream mesh workflows can consume clipped and simplified river products

Add and update tests that cover the new river workflow behavior, including archive handling and unified spherical river processing.

This includes moving the coastline docs into a unified mesh
section and some clean up to those docs as well.

Implement a config-driven sizing-field workflow for unified spherical meshes.

- move sizing-field configuration into the unified mesh package and discover mesh-specific settings from the unified mesh configs
- add the unified sizing-field task, build step, cell-width consumer, and visualization support so the workflow is wired end to end
- compose ocean, land, river, and coastline controls into a shared sizing-field product for downstream mesh generation
- add unified mesh family handling so specialized workflows such as the Southern Ocean mesh can reuse shared background-generation logic while default meshes stay generic

Add and update focused tests for the unified sizing-field workflow, including mesh-family coverage and recent fixes to the sizing-field composition behavior.