feat: cooking assistant can propose adding items to a shopping list

Second tool alongside createRecipe, same safety shape: addToShoppingList's
execute only validates/echoes input, no DB write. The proposal card lets
the user pick an existing list (fetched lazily) or name a new one, then
confirms through the exact two-call flow AddToShoppingListButton already
uses — POST /api/v1/shopping-lists (if new) then POST .../items — no new
persistence code path.

generateMealPlan intentionally not built as a tool: the existing
/api/v1/ai/meal-plan/generate endpoint generates and writes in one step
with a week/preferences input, not a specific plan payload, so it has no
"save this exact draft" entry point to confirm against without a larger
refactor. Documented as a known gap rather than forcing a weaker pattern.

v0.46.0

apps/web/app/api/v1/ai/cooking-chat/route.ts

@@ -9,6 +9,7 @@ import { getModelConfigForUseCase } from "@/lib/ai/resolve-user-key";
 import { resolveModel } from "@/lib/ai/factory";
 import { getUserPrivateBio, buildUserBioContext } from "@/lib/ai/user-bio";
 import { createRecipeTool } from "@/lib/ai/tools/create-recipe-tool";
+import { addToShoppingListTool } from "@/lib/ai/tools/add-to-shopping-list-tool";
 
 const Schema = z.object({
   question: z.string().min(1).max(500),
@@ -44,9 +45,9 @@ export async function POST(req: NextRequest) {
   const result = await withAiQuota(session!.user.id, session!.user.tier as "free" | "pro" | "team", () =>
     generateText({
       model,
-      system: `You are Epicure, a helpful culinary assistant answering general cooking questions — not tied to any specific recipe (techniques, substitutions, timing, equipment, food safety, etc). If asked who you are or what model/AI you're built on, say you're Epicure — never name the underlying model or provider. If a question has nothing to do with cooking or food, politely redirect. Keep answers under 200 words. Respond in ${lang}.\n\nYou can propose creating a recipe with the createRecipe tool when the user explicitly asks you to create, save, or write down a recipe — e.g. "make me a recipe for X" or "write that down as a recipe". Don't call it just because a recipe came up in conversation. When you do call it, still write a short text reply too (e.g. "Here's a draft — check it below and confirm if it looks right"), since calling the tool only drafts the recipe for the user to review; it never saves anything by itself.${bioContext}`,
+      system: `You are Epicure, a helpful culinary assistant answering general cooking questions — not tied to any specific recipe (techniques, substitutions, timing, equipment, food safety, etc). If asked who you are or what model/AI you're built on, say you're Epicure — never name the underlying model or provider. If a question has nothing to do with cooking or food, politely redirect. Keep answers under 200 words. Respond in ${lang}.\n\nYou have two tools, both of which only draft something for the user to review — neither saves anything by itself, so still write a short text reply too when you use one (e.g. "Here's a draft — check it below and confirm if it looks right").\n- createRecipe: only when the user explicitly asks you to create, save, or write down a recipe (e.g. "make me a recipe for X", "write that down as a recipe"). Don't call it just because a recipe came up in conversation.\n- addToShoppingList: only when the user explicitly asks to add ingredients/items to a shopping list (e.g. "add that to my shopping list").${bioContext}`,
       prompt: parsed.data.question,
-      tools: { createRecipe: createRecipeTool },
+      tools: { createRecipe: createRecipeTool, addToShoppingList: addToShoppingListTool },
       stopWhen: stepCountIs(3),
     }), { skipQuota: aiConfig.isByok }
   );
@@ -54,6 +55,7 @@ export async function POST(req: NextRequest) {
 
   const { conversationId } = parsed.data;
   const proposedRecipe = result.data.toolCalls.find((c) => c.toolName === "createRecipe")?.input;
+  const proposedShoppingList = result.data.toolCalls.find((c) => c.toolName === "addToShoppingList")?.input;
 
   void db.insert(chatMessages).values([
     { id: crypto.randomUUID(), userId: session!.user.id, recipeId: null, conversationId, role: "user", content: parsed.data.question },
@@ -72,5 +74,5 @@ export async function POST(req: NextRequest) {
     `).catch((err) => console.error("[cooking-chat] failed to touch conversation", err));
   }
 
-  return NextResponse.json({ answer: result.data.text, proposedRecipe });
+  return NextResponse.json({ answer: result.data.text, proposedRecipe, proposedShoppingList });
 }