refactor(gemini-client): rename and update initialization doc

Renamed DarwinAnthropic to DarwinGemini and updated documentation for clarity on the Gemini API client initialization process.

gemini-client/gemini-client-darwin/src/appleMain/kotlin/com/tddworks/gemini/api/DarwinGemini.kt

@@ -0,0 +1,27 @@
+package com.tddworks.gemini.api
+
+import com.tddworks.gemini.api.textGeneration.api.Gemini
+import com.tddworks.gemini.api.textGeneration.api.GeminiConfig
+import com.tddworks.gemini.di.initGemini
+
+/**
+ * A singleton object that initializes the Gemini configuration with the specified API key and base URL.
+ */
+object DarwinGemini {
+
+    /**
+     * Initializes the Gemini configuration with the specified API key and base URL.
+     *
+     * This function sets up the Gemini environment by creating a configuration using the provided
+     * API key and base URL, then initializing Gemini with this configuration.
+     *
+     * @param apiKey A lambda function that returns the API key as a string. Defaults to returning "CONFIG_API_KEY".
+     * @param baseUrl A lambda function that returns the base URL as a string. Defaults to returning `Gemini.BASE_URL`.
+     *
+     * @return The initialized Gemini configuration.
+     */
+    fun gemini(
+        apiKey: () -> String = { "CONFIG_API_KEY" },
+        baseUrl: () -> String = { Gemini.BASE_URL },
+    ) = initGemini(GeminiConfig(apiKey, baseUrl))
+}