feat: cooking assistant can propose creating a recipe

Gives the general chat a createRecipe tool (Vercel AI SDK, stepCountIs(3))
scoped so it can only ever produce a draft — the tool's execute is a pure
echo, no DB write. The route surfaces the tool call as proposedRecipe
alongside the normal text answer; the chat UI renders it as a card with
explicit Create/Discard buttons. Create POSTs to the existing
/api/v1/recipes endpoint — the same code path and tier/recipe-count limit
the manual editor already goes through — so there's exactly one place
that actually creates a recipe row, and nothing happens without the user
clicking Create.

Scoped to the general assistant only (not per-recipe chat), and to one
tool for now — addToShoppingList/generateMealPlan are follow-ups.

v0.45.0

apps/web/lib/ai/tools/create-recipe-tool.ts

@@ -0,0 +1,38 @@
+import { tool } from "ai";
+import { z } from "zod";
+
+const CreateRecipeInputSchema = z.object({
+  title: z.string().min(1).max(200),
+  description: z.string().max(2000).optional(),
+  baseServings: z.number().int().min(1).max(100).default(4),
+  recipeType: z.enum(["dish", "drink"]).default("dish"),
+  difficulty: z.enum(["easy", "medium", "hard"]).optional(),
+  prepMins: z.number().int().min(0).max(1440).optional(),
+  cookMins: z.number().int().min(0).max(1440).optional(),
+  ingredients: z.array(z.object({
+    rawName: z.string().min(1).max(200).describe("Ingredient name only, e.g. 'flour' — never combined with quantity/unit"),
+    quantity: z.number().optional().describe("A number only, e.g. 0.25, 1.5, 2"),
+    unit: z.string().max(50).optional().describe("e.g. 'cup', 'tbsp', 'g'"),
+  })).min(1).max(100),
+  steps: z.array(z.object({
+    instruction: z.string().min(1).max(2000),
+  })).min(1).max(100),
+});
+
+export type CreateRecipeToolInput = z.infer<typeof CreateRecipeInputSchema>;
+
+/**
+ * Lets the cooking assistant propose a new recipe from the conversation.
+ * Deliberately does NOT write to the database — `execute` just validates and
+ * echoes the input back as a draft. The chat UI renders that draft with an
+ * explicit Confirm button, which POSTs to the existing /api/v1/recipes
+ * endpoint (the same one the manual recipe editor uses) — so nothing gets
+ * created without the user directly approving it, and there's exactly one
+ * code path that actually writes a recipe row.
+ */
+export const createRecipeTool = tool({
+  description:
+    "Propose creating a new recipe based on the conversation. This only drafts the recipe for the user to review — it does not save anything. Only call this when the user has actually asked you to create/save/write down a recipe, not just discussed one.",
+  inputSchema: CreateRecipeInputSchema,
+  execute: async (input: CreateRecipeToolInput) => input,
+});