🧪 Add E2E tests for Storybook and Static-site SDKs

[Robdel12]

Context

PR #179 revealed that SDK integration tests weren't catching CLI changes that broke SDK compatibility. We've added a test-sdk-e2e CI job that always runs E2E tests for:

• ✅ Core JS Client (vizzlyScreenshot)
• ✅ Vitest SDK (toMatchScreenshot matcher)
• ✅ Ember SDK (vizzlyScreenshot helper)
• ✅ Ruby SDK (Vizzly.screenshot)

However, two SDKs still only have unit tests with mocked server responses:

• ❌ Storybook SDK
• ❌ Static-site SDK

What's needed

Storybook SDK E2E

Create a minimal test Storybook project that the SDK can crawl and capture screenshots from:

1. Add clients/storybook/test-storybook/ with a simple Storybook setup (2-3 stories)
2. Add npm run test:e2e script that runs the Storybook SDK against it
3. Add to test-sdk-e2e CI job

Static-site SDK E2E

Create a minimal test site that the SDK can crawl:

1. Add clients/static-site/test-site/ with a few HTML pages
2. Add npm run test:e2e script that runs the static-site SDK against it
3. Add to test-sdk-e2e CI job

Why this matters

These E2E tests ensure that changes to the CLI's TDD handler response format (like the status field changes in #169) are caught before they break SDK users.