This commit adds support for Perplexity AI provider (#3 - [Providers] Add Perplexity)

The following changes have been made:
Added the Perplexity provider to the GenAIProvider enum.
Updated the AI Assistance panel to handle the Perplexity provider, including loading and storing the API key, and populating the model dropdown with the available Perplexity models.
Created a PerplexityModelFetcher to provide the list of hardcoded models for Perplexity.
Updated the JeddictChatModelBuilder to use the OpenAI builders for the Perplexity provider, as the Perplexity API is OpenAI compatible.
Sorted the providers by name in the UI.
Improved error handling in the JeddictChatModelBuilder.
Refactored the layout of the AIAssistancePanel to better handle component resizing.

Author: stefanofornari

src/main/java/io/github/jeddict/ai/lang/JeddictChatModelBuilder.java

@@ -52,6 +52,7 @@
 import static io.github.jeddict.ai.settings.GenAIProvider.MISTRAL;
 import static io.github.jeddict.ai.settings.GenAIProvider.OLLAMA;
 import static io.github.jeddict.ai.settings.GenAIProvider.OPEN_AI;
+import static io.github.jeddict.ai.settings.GenAIProvider.PERPLEXITY;
 import io.github.jeddict.ai.settings.PreferencesManager;
 import java.time.Duration;
 import java.util.ArrayList;
@@ -100,7 +101,7 @@ public JeddictChatModelBuilder(JeddictStreamHandler handler, String modelName) {
                     case GOOGLE -> {
                         streamModel = buildModel(new GoogleStreamingBuilder(), modelName);
                     }
-                    case OPEN_AI, DEEPINFRA, DEEPSEEK, GROQ, CUSTOM_OPEN_AI,COPILOT_PROXY -> {
+                    case OPEN_AI, DEEPINFRA, DEEPSEEK, GROQ, CUSTOM_OPEN_AI, COPILOT_PROXY, PERPLEXITY -> {
                         streamModel = buildModel(new OpenAiStreamingBuilder(), modelName);
                     }
                     case MISTRAL -> {
@@ -125,7 +126,7 @@ public JeddictChatModelBuilder(JeddictStreamHandler handler, String modelName) {
                     case GOOGLE -> {
                         model = buildModel(new GoogleBuilder(), modelName);
                     }
-                    case OPEN_AI, DEEPINFRA, DEEPSEEK, GROQ, CUSTOM_OPEN_AI,COPILOT_PROXY -> {
+                    case OPEN_AI, DEEPINFRA, DEEPSEEK, GROQ, CUSTOM_OPEN_AI, COPILOT_PROXY, PERPLEXITY -> {
                         model = buildModel(new OpenAiBuilder(), modelName);
                     }
                     case MISTRAL -> {
@@ -308,6 +309,7 @@ private String generateInternal(Project project, String prompt, List<String> ima
                         "AI assistance failed to generate the requested response: " + errorMessage,
                         "Error in AI Assistance",
                         JOptionPane.ERROR_MESSAGE);
+                handler.onError(e);
             }
             handle.finish();
         }

src/main/java/io/github/jeddict/ai/models/PerplexityModelFetcher.java

@@ -0,0 +1,39 @@
+/**
+ * Copyright 2025 the original author or authors from the Jeddict project (https://jeddict.github.io/).
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package io.github.jeddict.ai.models;
+
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ *
+ */
+public class PerplexityModelFetcher {
+
+    public final String API_URL = "https://api.perplexity.ai";
+
+    public String getAPIUrl() {
+        return API_URL;
+    }
+
+    /**
+     * Perplexity does not support fetching the models for now, but we keep same
+     * pattern as per the other providers.
+     */
+    public List<String> getModels() {
+        return Arrays.asList("sonar", "sonar-pro", "sonar-reasoning", "sonar-reasoning-pro", "sonar-deep-research");
+    }
+}