Add WeatherKit data source package

Implements @aris/data-source-weatherkit for fetching weather data from
Apple WeatherKit REST API.

- WeatherKitDataSource class implementing DataSource interface
- Feed items: current, hourly, daily, and alerts
- Priority adjustment based on weather conditions and alert severity
- Unit conversion (metric/imperial)
- Response validation with arktype
- Test fixtures from real API responses

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

packages/aris-data-source-weatherkit/package.json

@@ -0,0 +1,14 @@
+{
+	"name": "@aris/data-source-weatherkit",
+	"version": "0.0.0",
+	"type": "module",
+	"main": "src/index.ts",
+	"types": "src/index.ts",
+	"scripts": {
+		"test": "bun test ."
+	},
+	"dependencies": {
+		"@aris/core": "workspace:*",
+		"arktype": "^2.1.0"
+	}
+}