fix(LLMModelManager): standardize GitHub branding and simplify model handling

- Fix inconsistent "Github" vs "GitHub" branding throughout codebase
- Remove redundant getModelIdFromProvider method
- Simplify model selection logic by using modelId directly
- Update getProviderNameFromModelId to return modelId for GitHub models

Author: phodal

core/src/main/kotlin/cc/unitmesh/devti/gui/chat/ui/AutoDevInputSection.kt

@@ -131,10 +131,9 @@ class AutoDevInputSection(
         modelSelector = JComboBox(modelItems.toTypedArray())
 
         val currentModel = AutoDevSettingsState.getInstance().defaultModelId.ifEmpty { "Default" }
-        val currentModelId = LLMModelManager.getInstance().getModelIdFromProvider(currentModel)
         for (i in 0 until modelSelector.itemCount) {
             val item = modelSelector.getItemAt(i)
-            if (item.modelId == currentModelId) {
+            if (item.modelId == currentModel) {
                 modelSelector.selectedIndex = i
                 break
             }

core/src/main/kotlin/cc/unitmesh/devti/settings/model/LLMModelManager.kt

@@ -36,10 +36,10 @@ class LLMModelManager(
      * Check if a model is custom (not GitHub Copilot)
      */
     fun isCustomLLM(modelName: String): Boolean {
-        // GitHub models start with "Github: "
-        if (modelName.startsWith("Github: ")) {
+        if (modelName.startsWith("GitHub: ")) {
             return false
         }
+
         val userModels = LlmConfig.load()
         return userModels.any { it.name == modelName }
     }
@@ -55,7 +55,7 @@ class LLMModelManager(
             val githubModels = manager.getSupportedModels(forceRefresh = false)
             githubModels?.forEach { model ->
                 models.add(ModelItem(
-                    displayName = "Github: ${model.id}",
+                    displayName = "GitHub: ${model.id}",
                     modelId = model.id,
                     isCustom = false
                 ))
@@ -74,24 +74,6 @@ class LLMModelManager(
         return models
     }
 
-    /**
-     * Get model ID from provider name
-     * Used by AutoDevInputSection to find current selected model
-     */
-    fun getModelIdFromProvider(providerName: String): String {
-        if (providerName.isEmpty() || providerName == "Default") {
-            return "Default"
-        }
-        
-        // For GitHub models, extract model ID from "Github: model-id" format
-        if (providerName.startsWith("Github: ")) {
-            return providerName.removePrefix("Github: ")
-        }
-        
-        // For custom models, the provider name is the model name
-        return providerName
-    }
-    
     /**
      * Get provider name from model ID
      * Used by AutoDevInputSection when model selection changes
@@ -107,7 +89,7 @@ class LLMModelManager(
             val githubModels = manager.getSupportedModels(forceRefresh = false)
             val isGithubModel = githubModels?.any { it.id == modelId } == true
             if (isGithubModel) {
-                return "Github: $modelId"
+                return modelId
             }
         }