Holos 4 - 16fee856

Fix sheep diet forage percentages and tests

Correct forage percentages for the three default sheep diets (Good/Average/Poor) from 0% to 85%, 97%, and 100% respectively. Changes update H.Core.Providers.Feed.DietProvider, the CSV resource Table_18_26_Diet_Coefficients_For_Beef_Dairy_Sheep.csv, add regression tests in H.Core.Test (DietProviderTest and SheepResultsServiceTest) to prevent regressions, and add a Changelog entry. This fixes an issue where forage=0 caused grain-in-diet=100 and an incorrect urinary energy coefficient (0.02) that underestimated volatile solids (should be 0.04). Files changed: H.Core/Providers/Feed/DietProvider.cs, H.Content/Resources/Table_18_26_Diet_Coefficients_For_Beef_Dairy_Sheep.csv, H.Core.Test/Providers/Feed/DietProviderTest.cs, H.Core.Test/Services/SheepResultsServiceTest.cs, Changelog.md.

See #424