Add Playwright E2E test suite with CI for intersection observer behavior

[Copilot]

Adds end-to-end testing infrastructure to validate intersection observer behavior: content loads only when scrolled into viewport and unloads when scrolled out.

Test Infrastructure

• Playwright suite with 7 tests covering viewport-based lazy loading, content unloading, infinite scroll, and sequential loading
• Express test server (tests/server.js) serving dynamic content via /api/load endpoint
• Local htmx.min.js bundled for offline test execution
• Tests use deterministic waits (waitForFunction, waitForResponse) rather than fixed timeouts

Test Page

tests/index.html demonstrates infinite scroll with:

• Initial items with hx-trigger="intersect" and intersect-unload="content"
• Dynamic load trigger that fires when scrolled into viewport
• Stats dashboard tracking loaded/unloaded state

<div class="item" 
     hx-ext="intersect"
     hx-trigger="intersect"
     intersect-unload="content"
     intersect-unload-delay="500">
  <h3>Item Content</h3>
</div>

CI Integration

GitHub Actions workflow (.github/workflows/test.yml) runs on push/PR with:

• Playwright browser installation
• Automatic webServer startup via Playwright config
• Explicit contents: read permission
• Test artifact upload on completion

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• unpkg.com
  • Triggering command: /home/REDACTED/.cache/ms-playwright/chromium_headless_shell-1208/chrome-headless-shell-linux64/chrome-headless-shell /home/REDACTED/.cache/ms-playwright/chromium_headless_shell-1208/chrome-headless-shell-linux64/chrome-headless-shell --disable-field-trial-config --disable-REDACTED-networking --disable-REDACTED-timer-throttling --disable-REDACTEDing-occluded-windows --disable-back-forward-cache --disable-breakpad --disable-client-side-phishing-detection --disable-component-extensions-with-REDACTED-pages --disable-component-update --no-default-browser-check --disable-default-apps --disable-dev-shm-usage --disable-extensions --disable-features=AvoidUnnecessaryBeforeUnloadCheckSync,BoundaryEventDispatchTracksNodeRemoval,DestroyProfileOnBrowserClose,DialMediaRouteProvider,GlobalMediaControls,HttpsUpgrades,LensOverlay,MediaRouter,PaintHolding,ThirdPartyStoragePartitioning,Transl (dns block)
  • Triggering command: /home/REDACTED/.cache/ms-playwright/chromium_headless_shell-1208/chrome-headless-shell-linux64/chrome-headless-shell /home/REDACTED/.cache/ms-playwright/chromium_headless_shell-1208/chrome-headless-shell-linux64/chrome-headless-shell --disable-field-trial-config --disable-REDACTED-networking --disable-REDACTED-timer-throttling --disable-REDACTEDing-occluded-windows --disable-back-forward-cache --disable-breakpad --disable-client-side-phishing-detection --disable-component-extensions-with-REDACTED-pages --disable-component-update --no-default-browser-check --disable-default-apps --disable-dev-shm-usage --disable-extensions --disable-features=AvoidUnnecessaryBeforeUnloadCheckSync,BoundaryEventDispatchTracksNodeRemoval,DestroyProfileOnBrowserClose,DialMediaRouteProvider,GlobalMediaControls,HttpsUpgrades,LensOverlay,MediaRouter,PaintHolding,ThirdPartyStoragePartitioning,Transl modules/@npmcli/run-script/lib/node-gyp-bin/node (dns block)
  • Triggering command: /usr/bin/curl curl -o tests/htmx.min.js REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Playwright test suite in CI</issue_title>
<issue_description>* Add github actions CI script

• implement "infinite scroll" content web server with necessary endpoints (load, unload etc)
• Add playwright test suite that tests basic library properties (content is loaded only when inside the viewport and unloaded otherwise)

Take inspiration from https://wanago.io/2024/04/29/react-infinite-scrolling-e2e-playwright/ for end-to-end web testing with playwright</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Playwright test suite in CI #1

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