feat(community/agents): add AL agent quality guidance

- add 20 agent knowledge rules with good and bad AL samples
- clarify setup dialog shape, temporary persistence, permissions, profiles, instructions, capability registration, and interface wiring
- add the community-owned AL agents review skill
- make review fixture discovery layer-aware with custom, community, and Microsoft precedence
- document layer-aware evaluation behavior

community/knowledge/agents/bind-agent-subscribers-only-in-agent-session.bad.al

@@ -0,0 +1,9 @@
+codeunit 50101 "Sales Review Agent Events"
+{
+    [EventSubscriber(ObjectType::Table, Database::"Sales Header", OnAfterInsertEvent, '', false, false)]
+    local procedure OnAfterInsertSalesHeader(var Rec: Record "Sales Header")
+    begin
+        // Runs for every user session, not only the agent.
+        Message('Keep going, agent.');
+    end;
+}