Playwright: use wp-env.json settings for its base URL, if available

[priethor]

What

Configure Playwright to read wp-env port and host from .wp-env.json or environment variables.

Why

• Playwright was hardcoded to connect to port 8889 instead of the actual wp-env test port, which causes conflicts if you are running multiple projects in parallel (like Gutenberg).
• BaseConfig's webServer was attempting to start wp-env automatically, which is unnecessary since GH actions already to it.

How

• Reading port and host from environment variables (WP_BASE_URL, WP_ENV_TESTS_PORT, WP_ENV_TESTS_HOST) if set
• Otherwise, reading testsPort and testsHost from .wp-env.json file
• Overriding use.baseURL with the configured URL
• Setting webServer: undefined to disable automatic server startup

Testing Instructions

Using .wp-env.json

1. Change the testsPort in wp-env and start it
2. Run tests: npm run test:e2e

Using environment variables

1. Set custom URL: WP_BASE_URL=http://localhost:9999 npm run test:e2e

[github-actions]

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Core Committers: Use this line as a base for the props when committing in SVN:

Props priethor.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 1.17%. Comparing base (bf37e58) to head (3b478a2).
⚠️ Report is 3 commits behind head on trunk.

Additional details and impacted files

@@           Coverage Diff           @@
##             trunk    #238   +/-   ##
=======================================
  Coverage     1.17%   1.17%           
  Complexity    4416    4416           
=======================================
  Files          261     261           
  Lines        27017   27017           
=======================================
  Hits           318     318           
  Misses       26699   26699           

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