Add reusable Playwright test harness

Summary

Add a reusable Playwright end-to-end test harness to this task module so Sampler-based repositories can run browser tests through the same build entry point and reporting conventions as their Pester tests.

Scope

• Add a shipped InvokeBuild task file under source/Tasks and export it through a Task.* alias and AliasesToExport metadata.
• Keep reusable helper logic in one-function-per-file module functions under source/Public or source/Private; do not add a sibling task PSM1.
• Provide Pester 5 wrapper tasks for importing Pester, running Playwright wrappers, failing the build on test failures, and a convenient testUI workflow alias.
• Support defaults-first configuration where invocation parameters override build.yaml, and build.yaml overrides module defaults.
• Default test discovery to tests/playwright, with configurable run paths, tags, and excluded tags.
• Write Pester NUnit XML results under output/playwright.
• Document a Node Playwright harness using package.json, playwright.config.ts, and browser test folders such as tests/smoke.
• Configure Playwright to retain traces, screenshots, and videos on failures and emit a JUnit result file under output/playwright.
• Define how npm ci and the required Playwright browser installation are bootstrapped locally and in CI.
• Keep secrets and target URLs environment-driven; no credentials should be committed.
• Add unit tests for configuration conversion, path resolution, filtering, and failure propagation.
• Add WikiSource documentation for consumer setup, configuration, task reference, output files, and CI integration.

Suggested task surface

• Import_Pester_For_Playwright
• Invoke_Playwright_Pester_Tests_v5
• Fail_Build_If_Playwright_Tests_Failed
• Playwright_Tests_Stop_On_Fail
• testUI

Acceptance criteria

• A consumer can add the module through RequiredModules.psd1, import its Task.* alias through ModuleBuildTasks, and run ./build.ps1 -Tasks testUI.
• Missing configured test paths fail with a clear actionable error.
• Playwright and Pester result files are generated in deterministic locations below output/playwright.
• Browser diagnostics are retained on failures and can be uploaded as CI artifacts.
• A failing browser test fails the InvokeBuild workflow.
• The harness works on supported PowerShell and GitHub-hosted runner environments.
• Public/private helper functions follow this repository's source layout and test conventions.
• Documentation describes the complete setup without depending on repository-specific application details.

Beginne damit, die bestehenden Pester-Task-Konventionen sowie die Layouts von source/Tasks, source/Public und source/Private zu überprüfen. Verfolge die Modul-Exporte über RequiredModules.psd1, Aliase von Task.* und AliasesToExport hinweg und untersuche anschließend build.yaml sowie die angeforderten Playwright-Dateien und Ausgabe-Pfade. Als abgeschlossen gilt die Aufgabe, wenn der testUI-Workflow, die Konfiguration und das Fehlerverhalten, die Diagnostik, die Unit-Tests, die CI-Einrichtung und die WikiSource-Dokumentation die aufgeführten Abnahmekriterien erfüllen.