chore: drop unnecessary null-forgiving operators + silence coverage warning

CI flagged 9 IDE0370 "Suppression is unnecessary" findings on the null-forgiving
operator (`!`) applied to return expressions in SemanticQuantity.cs and a
reflection call site in SemanticString.cs. Create<TResult>() is non-nullable
already, so the suppression is noise.

Also adds `if-no-files-found: ignore` to the Upload Coverage Report step so
runs that don't produce coverage don't surface a workflow warning.

https://claude.ai/code/session_01LqtywMUn5GwFATD5FDdLn6

Author: claude

.github/workflows/dotnet.yml

@@ -187,6 +187,7 @@ jobs:
           path: |
             ./coverage/*
           retention-days: 7
+          if-no-files-found: ignore
 
   winget:
     name: Update Winget Manifests

Semantics.Quantities/SemanticQuantity.cs

@@ -67,7 +67,7 @@ public static TResult Multiply<TResult>(SemanticQuantity<TStorage> self, Semanti
 	{
 		Ensure.NotNull(self);
 		Ensure.NotNull(other);
-		return Create<TResult>(self.Quantity * other.Quantity)!;
+		return Create<TResult>(self.Quantity * other.Quantity);
 	}
 
 	/// <summary>
@@ -81,7 +81,7 @@ public static TResult Multiply<TResult>(SemanticQuantity<TStorage> self, TStorag
 		where TResult : SemanticQuantity<TStorage>, new()
 	{
 		Ensure.NotNull(self);
-		return Create<TResult>(self.Quantity * other)!;
+		return Create<TResult>(self.Quantity * other);
 	}
 
 	/// <summary>
@@ -96,7 +96,7 @@ public static TResult Divide<TResult>(SemanticQuantity<TStorage> self, SemanticQ
 	{
 		Ensure.NotNull(self);
 		Ensure.NotNull(other);
-		return Create<TResult>(self.Quantity / other.Quantity)!;
+		return Create<TResult>(self.Quantity / other.Quantity);
 	}
 
 	/// <summary>
@@ -110,7 +110,7 @@ public static TResult Divide<TResult>(SemanticQuantity<TStorage> self, TStorage
 		where TResult : SemanticQuantity<TStorage>, new()
 	{
 		Ensure.NotNull(self);
-		return Create<TResult>(self.Quantity / other)!;
+		return Create<TResult>(self.Quantity / other);
 	}
 
 	/// <summary>
@@ -142,7 +142,7 @@ public static TResult Add<TResult>(SemanticQuantity<TStorage> self, SemanticQuan
 	{
 		Ensure.NotNull(self);
 		Ensure.NotNull(other);
-		return Create<TResult>(self.Quantity + other.Quantity)!;
+		return Create<TResult>(self.Quantity + other.Quantity);
 	}
 
 	/// <summary>
@@ -157,7 +157,7 @@ public static TResult Subtract<TResult>(SemanticQuantity<TStorage> self, Semanti
 	{
 		Ensure.NotNull(self);
 		Ensure.NotNull(other);
-		return Create<TResult>(self.Quantity - other.Quantity)!;
+		return Create<TResult>(self.Quantity - other.Quantity);
 	}
 
 	/// <summary>
@@ -170,7 +170,7 @@ public static TResult Negate<TResult>(SemanticQuantity<TStorage> self)
 		where TResult : SemanticQuantity<TStorage>, new()
 	{
 		Ensure.NotNull(self);
-		return Create<TResult>(-self.Quantity)!;
+		return Create<TResult>(-self.Quantity);
 	}
 
 	/// <inheritdoc/>

Semantics.Strings/SemanticString.cs

@@ -557,8 +557,8 @@ private static TDest FromStringInternal<TDest>(string? value)
 		Ensure.NotNull(value);
 
 		Type typeOfTDest = typeof(TDest);
-		TDest newInstance = (TDest)Activator.CreateInstance(type: typeOfTDest)!;
-		typeOfTDest.GetProperty(name: nameof(WeakString))!.SetValue(obj: newInstance, value: newInstance.MakeCanonical(value));
+		TDest newInstance = (TDest)Activator.CreateInstance(type: typeOfTDest);
+		typeOfTDest.GetProperty(name: nameof(WeakString)).SetValue(obj: newInstance, value: newInstance.MakeCanonical(value));
 		return newInstance;
 	}