Add Gravity API key button guidance

Author: jahooma

common/src/tools/params/tool/gravity-index.ts

@@ -22,6 +22,7 @@ Choose the action:
 Important setup-link behavior:
 - Search results include \`conversion_url\`, the setup link the user should visit to create an account and get API credentials.
 - Always show this link prominently as "Get your {service.name} API key" when credentials are needed.
+- If the user is at the step of integrating a new service and credentials are the next required action, use \`render_ui\` when available to show a primary button labeled "Get your {service.name} API key" with \`conversion_url\` as the link.
 - Do not replace it with the vendor homepage and do not auto-follow it.
 - Ask the user to paste the resulting credentials back so you can finish setup.