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/set-instructions-as-secrettext.good.al

@@ -0,0 +1,20 @@
+codeunit 50100 "Sales Review Agent Create"
+{
+    procedure CreateWithInstructions()
+    var
+        Agent: Codeunit Agent;
+        TempAgentAccessControl: Record "Agent Access Control" temporary;
+        AgentUserSecurityId: Guid;
+        Instructions: SecretText;
+        InstructionsNameTxt: Label 'Instructions.txt', Locked = true;
+    begin
+        AgentUserSecurityId := Agent.Create(
+            Enum::"Agent Metadata Provider"::"Sales Review Agent",
+            'SALESREVIEW',
+            'Sales Review Agent',
+            TempAgentAccessControl);
+        Instructions := NavApp.GetResourceAsText(InstructionsNameTxt);
+        Agent.SetInstructions(AgentUserSecurityId, Instructions);
+        Agent.Activate(AgentUserSecurityId);
+    end;
+}