feat(fast-test-harness): propagate shadow DOM options through template generation and SSR

[radium-v]

Pull Request

📖 Description

Adds support for shadow DOM options (e.g. delegatesFocus, mode) throughout the test harness template generation and SSR rendering pipeline, so SSR-rendered components produce declarative shadow roots that match their client-side definitions.

Also adds a url property to SSRFixture for tests that need to control the page URL during SSR rendering.

Key changes:

• Template generation now reads shadow options from component definitions and emits matching shadowrootmode / shadowrootdelegatesfocus attributes via a pluggable resolver (resolveShadowOptions).
• SSR rendering propagates shadow options through to the rendered output.
• SSRFixture gains a url option.

📑 Test Plan

• New unit tests cover the shadow-options resolution path in generate-templates and generate-webui-templates, plus SSR render behavior.
• New Playwright spec verifies the SSRFixture url property.
• All existing tests pass locally via npm run test -w @microsoft/fast-test-harness.

✅ Checklist

General

• I have included a change request file using $ npm run change
• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.