fix(coding): close PI-100 review findings

electron/coding-runtime/in-memory-conversation-runtime.ts

@@ -14,6 +14,7 @@ import type {
   ForkConversationInput,
   ForkResult,
   PrepareConversationInput,
+  ProductModelRef,
   PromptAcceptance,
   PromptConversationInput,
   QueueAcceptance,
@@ -316,6 +317,17 @@ export class InMemoryConversationRuntime implements CodingConversationRuntime {
     }, current.runId);
   }
 
+  async validateModel(model: ProductModelRef): Promise<ProductModelRef> {
+    if (!model.accountId.trim() || !model.modelId.trim()) {
+      throw new CodingRuntimeContractError(
+        'CODING_MODEL_UNAVAILABLE',
+        'The selected model is unavailable',
+        true,
+      );
+    }
+    return clone(model);
+  }
+
   async setModel(input: SetConversationModelInput): Promise<ConversationModelState> {
     const snapshot = this.snapshot(input.conversationId);
     const thinkingLevel = snapshot.conversation.model.model?.thinkingLevel ?? 'off';