knowledge(performance): add community rules for JIT, locks, and false positives

These articles capture BC-specific mechanics agents still invert: partial-record JIT on writes, Reset clearing SetLoadFields, HttpClient inside write transactions, and batched number series, plus negative guidance that stops over-eager Query and IsEmpty "fixes".

Co-authored-by: Cursor <cursoragent@cursor.com>

community/knowledge/performance/page-background-tasks-for-expensive-cues.good.al

@@ -0,0 +1,49 @@
+page 50100 "Cue Background Task Good"
+{
+    PageType = CardPart;
+    ApplicationArea = All;
+
+    layout
+    {
+        area(content)
+        {
+            cuegroup(Group)
+            {
+                field(OpenOrders; OpenOrderCount)
+                {
+                    Caption = 'Open Sales Orders';
+                }
+            }
+        }
+    }
+
+    var
+        OpenOrderCount: Integer;
+        TaskId: Integer;
+
+    trigger OnAfterGetCurrRecord()
+    var
+        Args: Dictionary of [Text, Text];
+    begin
+        CurrPage.EnqueueBackgroundTask(TaskId, Codeunit::"Cue Open Order Count", Args);
+    end;
+
+    trigger OnPageBackgroundTaskCompleted(CompletedTaskId: Integer; Results: Dictionary of [Text, Text])
+    begin
+        if Results.ContainsKey('Count') then
+            Evaluate(OpenOrderCount, Results.Get('Count'));
+    end;
+}
+
+codeunit 50100 "Cue Open Order Count"
+{
+    trigger OnRun()
+    var
+        SalesHeader: Record "Sales Header";
+        Results: Dictionary of [Text, Text];
+    begin
+        SalesHeader.SetRange("Document Type", SalesHeader."Document Type"::Order);
+        Results.Add('Count', Format(SalesHeader.CountApprox()));
+        Page.SetBackgroundTaskResult(Results);
+    end;
+}