A retyped endpoint no longer asks for the credential back

Loading models for an edited provider used to fall back to the values on screen
as soon as the upstream URL changed, which meant retyping a key that never
returns to the browser. The URL is now sent alongside the record, so only a
changed provider or a credential typed over the mask switches away from the
stored one.

src/pages/agent-network/providers.mdx

@@ -216,7 +216,8 @@ A few details worth knowing:
   still count toward the token caps.
 - **Editing a saved provider reuses the stored credential.** The API key (or, on Vertex AI,
   the uploaded service account key) never returns to your browser, so the lookup runs against
-  the credential already on the record. Change the provider, the upstream URL, or the masked
+  the credential already on the record. A retyped **Upstream URL** is sent with it, so a new
+  endpoint can be listed before it is saved. Change the provider or type over the masked
   credential and NetBird asks for a credential to use instead — the values on screen are
   then used.
 - **Bedrock ids are registered exactly as AWS issues them**, prefix included