feat: Add OAI_RESPONSES model provider and implement Responses API client tests

- Updated ModelProfile to include OAI_RESPONSES in the ModelProvider enum.
- Created CompletionClientTest to validate text and chat completion functionalities.
- Added ResponsesApiClientTest to test Responses API interactions, including model listing and conversation handling.
- Implemented ResponsesApiDialectTestConfiguration for managing reasoning efforts in tests.
- Updated application-test.properties to include a new profile for responses.
- Added local-responses.properties configuration for the Responses API.

src/main/java/de/extio/lmlib/client/Completion.java

@@ -3,8 +3,22 @@ package de.extio.lmlib.client;
 import java.math.BigDecimal;
 import java.time.Duration;
 import java.util.List;
+import java.util.Map;
 
-public final record Completion(String response, String reasoning, CompletionFinishReason finishReason, CompletionStatistics statistics, List<ToolCall> toolCalls) {
+/**
+ * Normalized result returned by lm-lib clients.
+ *
+ * @param response the assistant-visible text output
+ * @param reasoning the separately exposed reasoning summary or reasoning text
+ * @param finishReason why generation stopped
+ * @param statistics token, duration, cache, and cost accounting for the request
+ * @param toolCalls tool calls returned by the provider when the response stopped
+ *        for tool execution
+ * @param outputItems provider-specific structured output items that need to
+ *        survive follow-up rounds, primarily for stateless OpenAI Responses tool
+ *        loops
+ */
+public final record Completion(String response, String reasoning, CompletionFinishReason finishReason, CompletionStatistics statistics, List<ToolCall> toolCalls, List<Map<String, Object>> outputItems) {
 
 	public Completion {
 		response = response == null ? "" : response;
@@ -12,10 +26,22 @@ public final record Completion(String response, String reasoning, CompletionFini
 		finishReason = finishReason == null ? CompletionFinishReason.DONE : finishReason;
 		statistics = statistics == null ? new CompletionStatistics(0, Duration.ZERO, 0, 0, 0, 0, BigDecimal.ZERO, false) : statistics;
 		toolCalls = toolCalls == null ? List.of() : List.copyOf(toolCalls);
+		outputItems = outputItems == null ? List.of() : outputItems.stream().map(outputItem -> outputItem == null ? Map.<String, Object>of() : Map.copyOf(outputItem)).toList();
 	}
 
+	/**
+	 * Creates a completion without provider-specific output items.
+	 */
+	public Completion(final String response, final String reasoning, final CompletionFinishReason finishReason, final CompletionStatistics statistics, final List<ToolCall> toolCalls) {
+		this(response, reasoning, finishReason, statistics, toolCalls, List.of());
+	}
+
+	/**
+	 * Creates a plain text completion without tool calls or provider-specific
+	 * output items.
+	 */
 	public Completion(final String response, final String reasoning, final CompletionFinishReason finishReason, final CompletionStatistics statistics) {
-		this(response, reasoning, finishReason, statistics, List.of());
+		this(response, reasoning, finishReason, statistics, List.of(), List.of());
 	}
 
 }