Issue #3608483: Demo the webform request-validation examples and easy_email on the Tugboat preview

Closes #3608483 on drupal.org: https://www.drupal.org/project/orchestra/issues/3608483

Adds the webform request-validation examples and an email channel to the Tugboat preview, so it demonstrates the full form-driven, human-reviewed loop end to end.

• config.yml: add drupal/webform and drupal/easy_email to composer require (both are orchestra require-dev, so a path-repo install does not pull them). They are required in the build hook too (re-requiring drupal/orchestra by name in the same command), because an MR preview runs only the build hook and its detached-HEAD path repo offers orchestra as dev-main, which the base pin cannot satisfy on a re-resolve.
• setup.php: enable orchestra_interaction_webform_examples and orchestra_easy_email; the easy_email templates auto-activate from optional config.
• setup.php: turn on saving for the three request-validation email templates via setSaveEmail(TRUE), so the notifications are readable from the email log (/admin/reports/email).
• setup.php: the bilingual guide front page gains a Submission validation entry (English and French) linking /form/request-form and /form/request-form-link (webform hyphenates the default page path), plus the email log.

Companion bug fix (orchestra_easy_email), required for the above and a general fix: the notification channel called EmailHandler::sendEmail() with the save argument hardcoded to FALSE, so a template's "Save this email" setting was dead for every orchestra notification (no stored copy, empty email log). It now passes the template's getSaveEmail(), covered by a new EasyEmailChannelTest case (saved when the template opts in, not when it does not).

Verification: the module set is exercised by the examples Functional test; the easy_email save fix is covered by the kernel test above (green locally); setSaveEmail toggling confirmed against the real templates. The Tugboat build is the final check for the preview provisioning.