fix: use WebDriver new_window instead of JS window.open in tab_restart_browser

[vringar]

Summary

• Replace JS window.open('') with Selenium 4's webdriver.switch_to.new_window("tab") in tab_restart_browser()
• The old approach used a Selenium 3 workaround that breaks when popup-blocking prefs are active (e.g. dom.disable_open_during_load=True)
• Add regression test that enables popup blocking and runs two visits
• Document the previously-undocumented prefs field on BrowserParams

Closes #741
Closes #784

Test plan

• New test_get_with_popup_blocking passes locally
• Existing test_get_site_visits_table_valid still passes (both headless and xvfb)
• black, isort, mypy all clean
• CI passes

[Copilot]

Pull request overview

This PR fixes a browser restart issue where popup-blocking preferences break tab restarting. The fix replaces a legacy Selenium 3 workaround with Selenium 4's native new_window() method, which bypasses content-level popup blocking.

Changes:

• Replace JavaScript window.open('') with WebDriver's switch_to.new_window("window") in tab_restart_browser()
• Add regression test that enables popup blocking and verifies two visits complete successfully
• Document the previously-undocumented prefs field in BrowserParams configuration

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
openwpm/commands/browser_commands.py	Replaces JS-based window creation with WebDriver protocol to avoid popup blocking issues
test/test_simple_commands.py	Adds regression test verifying visits work with popup blocking enabled
docs/Configuration.md	Documents the prefs field for setting custom Firefox preferences

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.75%. Comparing base (40e044f) to head (e1cbbfb).
⚠️ Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1146      +/-   ##
==========================================
+ Coverage   56.62%   56.75%   +0.13%     
==========================================
  Files          40       40              
  Lines        3910     3908       -2     
==========================================
+ Hits         2214     2218       +4     
+ Misses       1696     1690       -6     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

The new expectations add cached image/css entries for the second visit, but test_cache_hits_recorded’s docstring later in this file still states that cached images do not trigger the relevant instrumentation events. To avoid confusion for future maintenance, please update/clarify that docstring (or the inline comment here) to match the new observed behavior (i.e., which cached resource types are expected to appear in http_requests/http_responses).

Suggested change

	# the shared HTTP cache (is_cached=1 in HTTP_CACHED_RESPONSES).
	# the shared HTTP cache (is_cached=1 in HTTP_CACHED_RESPONSES), but still
	# expected to generate entries in http_requests/http_responses (for both
	# the cached stylesheet and cached images).