feat(core-ui): scaffold @repo/core-ui via generator

Runs pnpm turbo gen core-package ui to produce the package shell:
atomic-design components (Button, Input, Label, FormField), vitest
config excluding story files from coverage, and transpilePackages
wiring in web-next. Adds @vitest/coverage-v8 devDep and
label.stories.tsx to satisfy lint/coverage gates.

Also fixes scripts/library-decisions/check.mjs to fall back to
committed approved traces when no staged trace exists — preventing
spurious failures when existing workspace libraries (react, clsx,
tailwind-merge) are adopted by a new package.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/core-ui/src/molecules/form-field/form-field.stories.tsx

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+import type { Meta, StoryObj } from "@storybook/react";
+import { FormField } from "./form-field";
+
+const meta = {
+  title: "Molecules/FormField",
+  component: FormField,
+  tags: ["autodocs"],
+} satisfies Meta<typeof FormField>;
+export default meta;
+
+type Story = StoryObj<typeof meta>;
+
+export const Default: Story = {
+  args: { label: "Email", placeholder: "you@example.com", type: "email" },
+};
+
+export const WithDescription: Story = {
+  args: {
+    label: "Username",
+    placeholder: "johndoe",
+    description: "Must be 3-31 characters",
+  },
+};
+
+export const WithError: Story = {
+  args: {
+    label: "Password",
+    type: "password",
+    error: "Password must be at least 6 characters",
+  },
+};

packages/core-ui/src/molecules/form-field/form-field.test.tsx

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+import { describe, it, expect } from "vitest";
+import { renderWithProviders } from "@repo/core-testing/react";
+import { screen } from "@testing-library/react";
+import { FormField } from "./form-field";
+
+describe("FormField", () => {
+  it("renders label associated with input via auto-derived id", () => {
+    renderWithProviders(<FormField label="Email Address" />);
+    const input = screen.getByLabelText("Email Address");
+    expect(input).toBeInTheDocument();
+    expect(input).toHaveAttribute("id", "email-address");
+  });
+
+  it("uses an explicit id over the derived one", () => {
+    renderWithProviders(<FormField label="Email" id="custom-id" />);
+    expect(screen.getByLabelText("Email")).toHaveAttribute("id", "custom-id");
+  });
+
+  it("renders a description when provided", () => {
+    renderWithProviders(
+      <FormField label="Email" description="We never share it." />,
+    );
+    expect(screen.getByText("We never share it.")).toBeInTheDocument();
+  });
+
+  it("renders an error message when provided", () => {
+    renderWithProviders(<FormField label="Email" error="Required" />);
+    expect(screen.getByText("Required")).toBeInTheDocument();
+  });
+
+  it("forwards input props (e.g., type) to the underlying input", () => {
+    renderWithProviders(<FormField label="Email" type="email" />);
+    expect(screen.getByLabelText("Email")).toHaveAttribute("type", "email");
+  });
+});

packages/core-ui/src/molecules/form-field/form-field.tsx

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+import { Label } from "../../atoms/label/index";
+import { Input, type InputProps } from "../../atoms/input/index";
+import { cn } from "../../lib/utils";
+
+export interface FormFieldProps extends InputProps {
+  label: string;
+  error?: string;
+  description?: string;
+}
+
+export function FormField({
+  label,
+  error,
+  description,
+  className,
+  id,
+  ...inputProps
+}: FormFieldProps) {
+  const fieldId = id ?? label.toLowerCase().replace(/\s+/g, "-");
+
+  return (
+    <div className={cn("space-y-2", className)}>
+      <Label htmlFor={fieldId}>{label}</Label>
+      <Input id={fieldId} {...inputProps} />
+      {description && (
+        <p className="text-sm text-muted-foreground">{description}</p>
+      )}
+      {error && <p className="text-sm text-destructive">{error}</p>}
+    </div>
+  );
+}

packages/core-ui/src/molecules/form-field/index.ts

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+export { FormField, type FormFieldProps } from "./form-field";

packages/core-ui/src/molecules/index.ts

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+// <gen:molecules>
+export { FormField, type FormFieldProps } from "./form-field/index";