Render all adapter field sections in the form with CSS :has(:checked)
controlling visibility. Selecting a provider instantly shows its config
fields — no JS, no page reload, no server round-trip needed.
- Render all 6 adapter configs with data-adapter attribute
- CSS :has(:checked) show/hide rules per adapter in admin stylesheet
- Namespace field names per adapter (email[brevo][api_key] etc)
- Drop 4 transactional-only providers (Resend, Postmark, Mailgun, MailPace)
- Remove noscript "Switch provider" button and controller redirect workaround
- Remove configured_adapter hidden input tracking
- Hide JS-only test email button for no-JS users via noscript style
- LiveView progressively enhances with async save and test email
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>