Refactor WeatherKit client to injectable interface

- Add WeatherKitClient interface and DefaultWeatherKitClient class
- WeatherKitDataSource accepts either client or credentials
- Simplify tests by injecting mock client directly
- Update fixture generation script to use new client class

Co-authored-by: Ona <no-reply@ona.com>

packages/aris-data-source-weatherkit/src/index.ts

@@ -26,10 +26,13 @@ export {
 	Certainty,
 	PrecipitationType,
 	ConditionCode,
+	DefaultWeatherKitClient,
 	type Severity as SeverityType,
 	type Urgency as UrgencyType,
 	type Certainty as CertaintyType,
 	type PrecipitationType as PrecipitationTypeType,
 	type ConditionCode as ConditionCodeType,
 	type WeatherKitCredentials,
+	type WeatherKitClient,
+	type WeatherKitQueryOptions,
 } from "./weatherkit"