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/use-dedicated-lookup-pages-not-full-lists.bad.al

@@ -0,0 +1,43 @@
+table 50100 "Campaign Member"
+{
+    Caption = 'Campaign Member';
+    // Full list as lookup runs FactBoxes and extra columns on every dropdown.
+    LookupPageId = Page::"Campaign Member List";
+    DrillDownPageId = Page::"Campaign Member List";
+    DataClassification = CustomerContent;
+
+    fields
+    {
+        field(1; "No."; Code[20]) { }
+        field(2; Name; Text[100]) { }
+        field(3; "Balance (LCY)"; Decimal) { }
+    }
+
+    keys
+    {
+        key(PK; "No.") { Clustered = true; }
+    }
+}
+
+page 50100 "Campaign Member List"
+{
+    PageType = List;
+    SourceTable = "Campaign Member";
+
+    layout
+    {
+        area(content)
+        {
+            repeater(Rows)
+            {
+                field("No."; Rec."No.") { }
+                field(Name; Rec.Name) { }
+                field("Balance (LCY)"; Rec."Balance (LCY)") { }
+            }
+        }
+        area(factboxes)
+        {
+            part(Details; "Campaign Member List") { }
+        }
+    }
+}