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/use-documented-instruction-keywords.good.al

@@ -0,0 +1,13 @@
+codeunit 50100 "Sales Review Agent Instr."
+{
+    procedure GetInstructions() Instructions: SecretText
+    var
+        Builder: TextBuilder;
+    begin
+        Builder.AppendLine('When the sales order is ready, request a review before posting.');
+        Builder.AppendLine('If a field is missing, ask for assistance.');
+        Builder.AppendLine('Memorize the customer credit limit for later steps.');
+        Builder.AppendLine('When confirmed, write an email to the salesperson; outbound mail is reviewed.');
+        Instructions := Builder.ToText();
+    end;
+}