fix(community/agents): align setup and permission samples

- mark agent setup pages as non-extensible where required
- narrow the agent profile by hiding an unrelated sales-order field
- define a dedicated read-only permission set for the sales review agent
- assign AL-defined permission sets with system scope and the owning app ID
- clarify the permission scope guidance for default access controls

community/knowledge/agents/agent-profile-narrows-visible-ui.good.al

@@ -8,6 +8,14 @@ profile "SALES REVIEW AGENT"
 
 pagecustomization "Sales Review Agent Sales Ord." customizes "Sales Order"
 {
+    layout
+    {
+        modify("Payment Terms Code")
+        {
+            Visible = false;
+        }
+    }
+
     actions
     {
         modify(Post)