fix(FXC-6541): keep default names for UI, write empty string in translator

- Remove Optional from SurfaceOutput.name and TimeAverageSurfaceOutput.name
  since they always have a string default
- Translator writes empty string to solver JSON for default names so the
  C++ solver falls back to the standard "surface" prefix
- Fix surface_output_class type annotations to use Type[]
- Restore name="Surface output" in services.py default params
- Re-sort service_init ref files for CI compatibility

Made-with: Cursor

Author: NasserFlexCompute

flow360/component/simulation/outputs/outputs.py

@@ -469,8 +469,8 @@ class SurfaceOutput(_AnimationAndFileFormatSettings, _OutputBase):
     # pylint: disable=fixme
     # TODO: entities is None --> use all surfaces. This is not implemented yet.
 
-    name: Optional[FileNameString] = pd.Field(
-        None,
+    name: FileNameString = pd.Field(
+        "Surface output",
         description="Name of the `SurfaceOutput`. Used as a suffix in output filenames to "
         "disambiguate when multiple outputs share the same surface entity. "
         "Must be unique across all instances that share the same surface.",
@@ -501,7 +501,7 @@ class SurfaceOutput(_AnimationAndFileFormatSettings, _OutputBase):
     @property
     def has_default_name(self) -> bool:
         """Whether this output has no custom name assigned."""
-        return self.name is None
+        return self.name == type(self).model_fields["name"].default
 
     @contextual_field_validator("entities", mode="after")
     @classmethod
@@ -545,8 +545,8 @@ class TimeAverageSurfaceOutput(SurfaceOutput):
     ====
     """
 
-    name: Optional[FileNameString] = pd.Field(
-        None,
+    name: FileNameString = pd.Field(
+        "Time average surface output",
         description="Name of the `TimeAverageSurfaceOutput`. Used as a suffix in output filenames "
         "to disambiguate when multiple outputs share the same surface entity. "
         "Must be unique across all instances that share the same surface.",

flow360/component/simulation/services.py

@@ -195,6 +195,7 @@ def get_default_params(
         reference_geometry = _get_default_reference_geometry(project_length_unit)
         operating_condition = AerospaceCondition(velocity_magnitude=dummy_value)
         surface_output = SurfaceOutput(
+            name="Surface output",
             entities=[Surface(name="*")],
             output_fields=["Cp", "yPlus", "Cf", "CfVec"],
         )

flow360/component/simulation/translator/solver_translator.py

@@ -597,7 +597,7 @@ def _translate_single_surface_output(
         ),
     )
     surface_output["writeSingleFile"] = output_instance.write_single_file
-    surface_output["name"] = output_instance.name if output_instance.name is not None else ""
+    surface_output["name"] = "" if output_instance.has_default_name else output_instance.name
     return surface_output