test: add unit and component tests across the monorepo

Adds ~1000 tests to bring the previously-untested packages and apps
under coverage:

- packages/utils — string, color, date, file, level, locale, sanitize,
  field, html, network-icons, rate-limit, url, url-security, monorepo,
  resume/patch, resume/docx/link-utils, style helpers (~97% on the
  testable utility files)
- packages/ui — 28 component test files plus the use-controlled-state,
  use-mobile, use-confirm, use-prompt hooks (95% statements)
- packages/pdf — shared template helpers (filtering, columns, picture,
  metrics, section-links, page-size, rich-text-html, section-title)
- packages/schema — resumeDataSchema, page, templates, default
- packages/fonts — expanded coverage on font helpers
- packages/ai — resume sanitize and extraction template
- packages/api — resume-access-policy
- apps/web — error-message, locale, theme, pwa, dialogs/store, and
  the resume/move-item / section-actions / make-section-item helpers

Adds jsdom polyfills (ResizeObserver, IntersectionObserver,
scrollIntoView, matchMedia) and an explicit React Testing Library
cleanup hook to vitest.setup.ts so portal- and overlay-based components
work without per-test setup.

packages/ui/src/components/button.test.tsx

@@ -0,0 +1,85 @@
+import { render, screen } from "@testing-library/react";
+import userEvent from "@testing-library/user-event";
+import { describe, expect, it, vi } from "vitest";
+import { Button } from "./button";
+
+describe("Button", () => {
+	it("renders children", () => {
+		render(<Button>Click me</Button>);
+		expect(screen.getByRole("button", { name: "Click me" })).toBeInTheDocument();
+	});
+
+	it("defaults to type='button' to prevent accidental form submits", () => {
+		render(<Button>Submit</Button>);
+		expect(screen.getByRole("button")).toHaveAttribute("type", "button");
+	});
+
+	it("respects an explicit type override", () => {
+		render(<Button type="submit">Submit</Button>);
+		expect(screen.getByRole("button")).toHaveAttribute("type", "submit");
+	});
+
+	it("applies the data-slot attribute for shadcn/base-ui slotting", () => {
+		render(<Button>x</Button>);
+		expect(screen.getByRole("button")).toHaveAttribute("data-slot", "button");
+	});
+
+	it("merges custom className with variant classes", () => {
+		render(<Button className="my-custom-class">x</Button>);
+		expect(screen.getByRole("button")).toHaveClass("my-custom-class");
+	});
+
+	it("calls onClick when clicked", async () => {
+		const onClick = vi.fn();
+		render(<Button onClick={onClick}>Click</Button>);
+		await userEvent.click(screen.getByRole("button"));
+		expect(onClick).toHaveBeenCalledOnce();
+	});
+
+	it("does not fire onClick when disabled", async () => {
+		const onClick = vi.fn();
+		render(
+			<Button disabled onClick={onClick}>
+				Click
+			</Button>,
+		);
+		await userEvent.click(screen.getByRole("button"));
+		expect(onClick).not.toHaveBeenCalled();
+	});
+
+	it("renders disabled state", () => {
+		render(<Button disabled>x</Button>);
+		expect(screen.getByRole("button")).toBeDisabled();
+	});
+
+	it.each([
+		["default"],
+		["outline"],
+		["secondary"],
+		["ghost"],
+		["destructive"],
+		["link"],
+	] as const)("renders variant=%s without throwing", (variant) => {
+		render(<Button variant={variant}>x</Button>);
+		expect(screen.getByRole("button")).toBeInTheDocument();
+	});
+
+	it.each([
+		["default"],
+		["xs"],
+		["sm"],
+		["lg"],
+		["icon"],
+		["icon-xs"],
+		["icon-sm"],
+		["icon-lg"],
+	] as const)("renders size=%s without throwing", (size) => {
+		render(<Button size={size}>x</Button>);
+		expect(screen.getByRole("button")).toBeInTheDocument();
+	});
+
+	it("forwards aria-label", () => {
+		render(<Button aria-label="Close">×</Button>);
+		expect(screen.getByRole("button", { name: "Close" })).toBeInTheDocument();
+	});
+});