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/instruction-structure-is-role-rules-steps.bad.al

@@ -0,0 +1,9 @@
+codeunit 50100 "Sales Review Agent Instr."
+{
+    procedure GetInstructions() Instructions: SecretText
+    var
+        PromptLbl: Label 'Check customer credit for the given sales order. Document the result.', Locked = true;
+    begin
+        Instructions := PromptLbl;
+    end;
+}