test: fix broken unit tests, add missing fixtures, and stabilize CI pipeline

- Fix os module mock pattern for Vitest v4 in proxy-ide-config tests

- Fix enterprise oauth_client_key expectations in cloudHandler-sync and token-manager-parity tests

- Fix proxy-controller integration test argument expectations

- Add missing proxy-parity JSON fixtures (OpenAI tools, Anthropic tool-use, Gemini SSE)

- Add reasoning_content mapping to convertClaudeToOpenAIResponse

- Fix google-api service test env var cache leak with resetModules + dynamic imports

- Fix proxy-metrics timer tests by calling onModuleInit in beforeEach

- Fix locale-sensitive number formatting in StatCard tests

- Add missing test files to version control (components, hooks, ipc, mocks, server, utils)

- Fix CI workflows: testing.yaml (use vitest run, add type-check job, npm cache), lint.yaml and format.yaml (add npm cache, concurrency, fix job names)

src/tests/unit/components/ui/button.test.tsx

@@ -0,0 +1,72 @@
+import React from 'react';
+import { screen, fireEvent } from '@testing-library/react';
+import { renderWithProviders } from '@/tests/unit/test-utils';
+import { Button, buttonVariants } from '@/components/ui/button';
+
+describe('Button', () => {
+  it('renders with default variant and size', () => {
+    renderWithProviders(<Button>Click me</Button>);
+    const button = screen.getByRole('button', { name: /click me/i });
+    expect(button).toBeInTheDocument();
+    expect(button).toHaveAttribute('data-slot', 'button');
+  });
+
+  it('renders all variant styles', () => {
+    const variants = ['default', 'destructive', 'outline', 'secondary', 'ghost', 'link'] as const;
+    variants.forEach((variant) => {
+      const { container } = renderWithProviders(
+        <Button variant={variant}>{variant}</Button>,
+      );
+      expect(container.querySelector('button')).toBeInTheDocument();
+    });
+  });
+
+  it('renders all size styles', () => {
+    const sizes = ['default', 'sm', 'lg', 'icon'] as const;
+    sizes.forEach((size) => {
+      const { container } = renderWithProviders(
+        <Button size={size}>{size}</Button>,
+      );
+      expect(container.querySelector('button')).toBeInTheDocument();
+    });
+  });
+
+  it('handles click events', () => {
+    const handleClick = vi.fn();
+    renderWithProviders(<Button onClick={handleClick}>Click me</Button>);
+    fireEvent.click(screen.getByRole('button'));
+    expect(handleClick).toHaveBeenCalledTimes(1);
+  });
+
+  it('supports disabled state', () => {
+    renderWithProviders(<Button disabled>Disabled</Button>);
+    expect(screen.getByRole('button')).toBeDisabled();
+  });
+
+  it('renders as child element when asChild is true', () => {
+    renderWithProviders(
+      <Button asChild>
+        <a href="/test">Link Button</a>
+      </Button>,
+    );
+    const link = screen.getByRole('link', { name: /link button/i });
+    expect(link).toBeInTheDocument();
+    expect(link).toHaveAttribute('href', '/test');
+  });
+
+  it('applies custom className', () => {
+    renderWithProviders(<Button className="custom-class">Styled</Button>);
+    expect(screen.getByRole('button')).toHaveClass('custom-class');
+  });
+
+  it('buttonVariants function returns expected classes for default variant', () => {
+    const classes = buttonVariants({ variant: 'default', size: 'default' });
+    expect(classes).toContain('bg-primary');
+    expect(classes).toContain('text-primary-foreground');
+  });
+
+  it('buttonVariants function returns expected classes for destructive variant', () => {
+    const classes = buttonVariants({ variant: 'destructive' });
+    expect(classes).toContain('bg-destructive');
+  });
+});