feat: Port ILLMProvider interface and langchain gemini adapter

packages/llm/src/index.ts

@@ -1 +1 @@
-export {};
+export * from "./llm.js";

packages/llm/src/llm.ts

@@ -0,0 +1,22 @@
+import { z } from "zod";
+
+export interface LLMRequest<T extends z.ZodTypeAny> {
+  systemPrompt: string;
+  userContext: string;
+  schema: T; // The Zod schema
+  temperature?: number;
+}
+
+export interface LLMResponse<T> {
+  success: boolean;
+  data?: T;
+  error?: string;
+}
+
+export interface ILLMProvider {
+  providerName: string;
+  // We use Zod to ensure the generic T matches the schema
+  generateStructuredResponse<T extends z.ZodTypeAny>(
+    request: LLMRequest<T>,
+  ): Promise<LLMResponse<z.infer<T>>>;
+}

packages/llm/src/providers/google-genai.ts

@@ -0,0 +1,26 @@
+import { z } from "zod";
+import { ChatGoogleGenerativeAI } from "@langchain/google-genai";
+import { ILLMProvider, LLMRequest, LLMResponse } from "../llm.js";
+
+export class GeminiProvider implements ILLMProvider {
+  providerName = "Gemini";
+  private model: ChatGoogleGenerativeAI;
+
+  constructor(apiKey: string) {
+    this.model = new ChatGoogleGenerativeAI({
+      apiKey,
+      model: "gemini-3-flash",
+    });
+  }
+
+  async generateStructuredResponse<T extends z.ZodTypeAny>(
+    request: LLMRequest<T>,
+  ): Promise<LLMResponse<z.infer<T>>> {
+    const structuredModel = this.model.withStructuredOutput(request.schema);
+    const result = await structuredModel.invoke([
+      { role: "system", content: request.systemPrompt },
+      { role: "user", content: request.userContext },
+    ]);
+    return { success: true, data: result as z.infer<T> };
+  }
+}