feat: Adds heat pump heating interpolation.

Tests/ManualSTests/ManualSTests.swift

@@ -138,6 +138,27 @@ struct ManualSTests {
     }
   }
 
+  @Test
+  func heatPumpHeatingInterpolation() async throws {
+    try await withDependencies {
+      $0.manualS = .liveValue
+    } operation: {
+      @Dependency(\.manualS) var manualS
+
+      let response = try await manualS.heatPumpHeatingInterpolation(.init(
+        winterDesignTemperature: 5,
+        heatLoss: 49667,
+        climateType: .mildWinterOrLatentLoad,
+        capacity: .mock
+      ))
+
+      #expect(response.finalCapacity == .mock)
+      #expect(response.capacityAtDesign == 11308)
+      #expect(response.balancePointTemperature == 38)
+      #expect(response.supplementalHeatRequired == 11)
+    }
+  }
+
   @Test
   func balancePoint() async throws {
     try await withDependencies {
@@ -351,3 +372,7 @@ extension Capacity.Cooling {
 extension DesignInfo.Summer {
   static let mock = Self(outdoorTemperature: 90, indoorTemperature: 75, indoorHumidity: 50)
 }
+
+extension Capacity.HeatPumpHeating {
+  static let mock = Self(at47: 24600, at17: 15100)
+}