Add community guidance and review support for Business Central agents (#137)

* 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

* 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

* Address agent review feedback

community/knowledge/agents/reapply-resource-instructions-on-upgrade.good.al

@@ -0,0 +1,33 @@
+codeunit 50100 "Sales Review Agent Upgrade"
+{
+    Subtype = Upgrade;
+
+    trigger OnUpgradePerCompany()
+    var
+        Agent: Codeunit Agent;
+        UpgradeTag: Codeunit "Upgrade Tag";
+        Instructions: SecretText;
+        AgentUserSecurityIds: List of [Guid];
+        AgentUserSecurityId: Guid;
+        TagTxt: Label 'SALESREVIEW-INSTR-2.0.0', Locked = true;
+        InstructionsNameTxt: Label 'Instructions.txt', Locked = true;
+    begin
+        if UpgradeTag.HasUpgradeTag(TagTxt) then
+            exit;
+        Instructions := NavApp.GetResourceAsText(InstructionsNameTxt);
+        AgentUserSecurityIds := GetExistingAgentUserIds();
+        foreach AgentUserSecurityId in AgentUserSecurityIds do
+            Agent.SetInstructions(AgentUserSecurityId, Instructions);
+        UpgradeTag.SetUpgradeTag(TagTxt);
+    end;
+
+    local procedure GetExistingAgentUserIds() AgentUserSecurityIds: List of [Guid]
+    var
+        SalesReviewAgentSetup: Record "Sales Review Agent Setup";
+    begin
+        if SalesReviewAgentSetup.FindSet() then
+            repeat
+                AgentUserSecurityIds.Add(SalesReviewAgentSetup."User Security ID");
+            until SalesReviewAgentSetup.Next() = 0;
+    end;
+}