fix(checkout): commit JS validation fix for auto-generate-password forms

[superdav42]

Problem

After PR #737 (simple checkout form template) merged, inc/checkout/class-checkout.php has an uncommitted fix sitting on main.

The fix adds form_has_auto_generate_password() method and uses it in get_js_validation_rules() to strip password-related JS validation rules when the checkout form uses auto-generated passwords. Without this, the JS validator requires a password field that is never rendered, blocking form submission.

What to do

1. Create a worktree from main
2. Implement the fix: add form_has_auto_generate_password(): bool protected method that iterates form settings to detect password fields with auto_generate_password enabled
3. In get_js_validation_rules(), call this method and unset($raw_rules['password'], $raw_rules['password_conf'], $raw_rules['valid_password']) when true
4. Commit and open a PR

Branch feature/738-simple-checkout-followup-fixes on origin has a similar implementation for reference.

Acceptance Criteria

• form_has_auto_generate_password() method exists in Checkout class
• get_js_validation_rules() strips password rules when auto-generate is enabled
• PR passes CI

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[superdav42]

Implemented and merged via PR #742 (commit bbad652).

What was done:

• Added form_has_auto_generate_password(): bool protected method to Checkout class — iterates form settings to detect password fields with auto_generate_password enabled
• Updated get_js_validation_rules() to call this method and unset($raw_rules['password'], $raw_rules['password_conf'], $raw_rules['valid_password']) when auto-generate is active
• All CI checks passed (PHP 8.2–8.5, Cypress, Code Quality, PHP Lint)

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