Stabilize Windows Behat failures in scaffold package/readme scenarios

[Copilot]

The failing Windows Behat job was caused by two separate issues:

1. README scenarios relying on live remote content for support-body rendering.
2. Windows path handling for --dir values expanded from ~/... with HOME set to an absolute Windows path.

This PR stabilizes both paths while keeping the test intent focused.

• Scope of change

  • Updated two scaffold package-readme scenarios in features/scaffold-package-readme.feature to:
    • create a minimal foo/composer.json fixture with the desired wp-cli/wp-cli requirement
    • run wp scaffold package-readme foo directly
  • Adjusted expected composer.json assertions in those scenarios to match fixture-based input/output.
  • Added HTTP response mocking for remote support-body README scenarios so they no longer depend on live network content.
  • Fixed Windows absolute-path detection in src/ScaffoldPackageCommand.php so backslash-based paths (e.g. C:\...) are correctly treated as absolute and not incorrectly prefixed with cwd.

• Why this resolves the failure

  • These README scenarios are intended to validate README/composer version messaging behavior, not full package scaffolding or package-loading behavior.
  • Using direct package-readme fixtures removes fragile package-loading behavior from those tests.
  • Mocking remote response bodies removes network/content volatility from README support-body scenarios.
  • Correct Windows absolute-path detection fixes tilde/HOME scaffold path failures on Windows.

• Targeted scenario update (example)

  - When I run `wp scaffold package wp-cli/foo --dir=foo --require_wp_cli='>=0.24.0-alpha' --skip-install`
  + And a foo/composer.json file:
  +   """
  +   {
  +       "name": "wp-cli/foo",
  +       "require": {
  +           "wp-cli/wp-cli": ">=0.24.0-alpha"
  +       }
  +   }
  +   """
  + When I run `wp scaffold package-readme foo`

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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