docs: fix the local development anchor and the propagation claim

Two claims on the custom claims and RBAC guide that leave a reader with
a wrong outcome.

The "local development" link pointed at
/docs/guides/auth/auth-hooks#local-development, and no heading by that
name exists. The section is "Developing", so the one link that carries
the local `config.toml` setting dropped the reader at the top of the
page. Renaming the heading restores the anchor rather than repointing
the link, because the Slack Clone example's own `config.toml` comment
expects the same anchor in two places. Nothing links to `#developing`.

The conclusion said the setup "automatically propagates to Supabase
Auth", which reads as though a role change reaches open sessions. It
reaches the next token the hook issues. Say when a change lands and how
to make it land now.

apps/docs/content/guides/api/custom-claims-and-role-based-access-control-rbac.mdx

@@ -199,7 +199,9 @@ For server-side logic, you can use a JWT package for your language, such as [`ex
 
 ## Conclusion
 
-You now have a robust system in place to manage user roles and permissions within your database that automatically propagates to Supabase Auth.
+You now have a system for managing user roles and permissions in your database, and the Auth Hook copies a user's role into every access token it issues.
+
+A role change reaches a user the next time their access token is issued, not immediately. Sessions that are already open keep the role they were issued with until the client refreshes them. To apply a role change right away, refresh the session with [`refreshSession()`](/docs/reference/javascript/auth-refreshsession) or have the user sign in again. See [Sessions](/docs/guides/auth/sessions) for how long an access token lasts.
 
 ## More resources
 

apps/docs/content/guides/auth/auth-hooks.mdx

@@ -134,7 +134,7 @@ Deno.serve(async (req) => {
 
 ## Using Hooks
 
-### Developing
+### Local development
 
 Let us develop a Hook locally and then deploy it to the cloud. As a recap, here’s a list of available Hooks