refactor(client): drop agentikHttpClient factory, accept HttpClient directly

- Remove agentikHttpClient(engineFactory: HttpClientEngineFactory<T>, ...)
  factory from :client; the typed factory parameter pulled engine-specific
  config (HttpClientConfig<T>.engine { ... }) and made the library's
  factory API look engine-coupled even though the factory itself was
  engine-agnostic.
- KDoc and SseTimeout no longer reference CIO as the canonical example.
- :client still exports applyAgentikDefaults(HttpClientConfig<*>) extension;
  consumers build HttpClient themselves with their chosen engine.
- :agentik-cli/defaultCliHttpClient updated to construct HttpClient(CIO)
  itself and apply agentik defaults inline; CIO-specific config
  (requestTimeout = 0) stays in the same block.

agentik-cli/src/commonMain/kotlin/pw/binom/agentik/cli/AgentikHttpClient.kt

@@ -2,12 +2,12 @@ package pw.binom.agentik.cli
 
 import io.ktor.client.HttpClient
 import io.ktor.client.engine.cio.CIO
-import pw.binom.agentik.client.agentikHttpClient
+import pw.binom.agentik.client.applyAgentikDefaults
 
 /**
  * HTTP-клиент CLI: движок CIO + конфигурация agentik.
  *
- * Движок живёт здесь, а не в `:client`: библиотека не выбирает транспорт за
+ * Движок выбирается здесь, а не в `:client`: библиотека не выбирает транспорт за
  * потребителя. Таргеты `:agentik-cli` (jvm + linuxX64/macosX64/macosArm64/mingwX64)
  * покрываются CIO.
  *
@@ -18,6 +18,7 @@ import pw.binom.agentik.client.agentikHttpClient
  * [token] = `null` — авторизация выключена.
  */
 internal fun defaultCliHttpClient(token: String? = null): HttpClient =
-    agentikHttpClient(engineFactory = CIO, token = token) {
+    HttpClient(CIO) {
+        applyAgentikDefaults(token)
         engine { requestTimeout = 0 }
-    }
+    }