[FXC-4069] Allow AutomatedFarfield with CustomVolume

[alexxu-flex]

user must specify exactly one outer CustomVolume using AutomatedFarfield and exterior geometry surfaces

still buggy (cursor comments and beyond), needs fixing

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Note

Medium Risk
Touches meshing validation and translation logic around farfield zone identification; misconfiguration could lead to wrong zone naming/patch lists and mesher failures, but changes are scoped and covered by new tests.

Overview
Allows AutomatedFarfield to be combined with CustomZones by introducing a farfield ghost boundary marker on exactly one CustomVolume to identify the exterior zone.

Validation now enforces that exactly one CustomVolume includes AutomatedFarfield.farfield (or its expanded GhostSphere/GhostCircularPlane forms), and CustomVolume is treated as compatible with the auto farfield method when using the beta mesher.

The volume-meshing translator skips ghost farfield entities from the patches list and renames the marked exterior custom volume to farfield in the translated zones output; tests were updated/added to cover these scenarios and error cases.

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[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

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[cursor]

Ghost surface filter unintentionally catches WindTunnelGhostSurface via inheritance

Medium Severity

WindTunnelGhostSurface inherits from GhostSurface, so the isinstance(surface, (GhostSurface, GhostSphere, GhostCircularPlane)) check inadvertently matches WindTunnelGhostSurface instances too. This causes wind tunnel ghost surface boundaries (e.g., windTunnelLeft, windTunnelRight) to be silently dropped from the patches list when a CustomVolume uses them as boundaries with WindTunnelFarfield. Previously, all boundary names were included in patches. The comment correctly says "AutomatedFarfield ghost entities," but the code is broader than intended due to inheritance.

 

[cursor]

Validator triggers incorrectly for CustomZones without CustomVolume

Low Severity

The guard condition has_custom_zones checks whether any CustomZones exists, but the comment and intent say "If AutomatedFarfield is used with CustomVolume(s)." If CustomZones contains only SeedpointVolume entities (no CustomVolume), the inner loop finds no matching CustomVolume, farfield_custom_volumes stays empty, and the validator raises a spurious error requiring a CustomVolume with the farfield ghost — even though there are no CustomVolume entities to validate. The condition needs to check for the presence of actual CustomVolume entities, not just CustomZones.