Add new action skills for AL testing and documentation

- Introduced `al-test-writer` to generate AL test codeunits for production objects based on TDD principles.
- Added `al-userguide-test-writer` to create test codeunits from user guide steps, mapping actions and assertions.
- Implemented `bc-extension-test-guide` to generate a comprehensive TEST_GUIDE.md for Business Central extensions, covering various categories.
- Created `bc-webclient-runner` to automate UI testing of the Business Central web client, capturing screenshots and asserting UI states.
- Developed `page-scripting-e2e` to produce a recording plan for Page Scripting, ensuring a structured approach to browser-level testing.

custom/knowledge/integration/never-call-external-services-from-posting.bad.al

@@ -0,0 +1,33 @@
+// Anti-pattern: the posting subscriber calls an external service INLINE, inside the
+// posting transaction. The post now holds document and ledger locks until the remote
+// endpoint answers, and a remote failure rolls the whole post back.
+
+codeunit 50112 "Post Shipment Notifier Bad"
+{
+    [EventSubscriber(ObjectType::Codeunit, Codeunit::"Sales-Post", 'OnAfterPostSalesDoc', '', false, false)]
+    local procedure NotifyShipmentInline(var SalesHeader: Record "Sales Header")
+    var
+        Client: HttpClient;
+        Content: HttpContent;
+        Response: HttpResponseMessage;
+    begin
+        Content.WriteFrom(BuildShipmentJson(SalesHeader));
+
+        // BAD: HttpClient.Post runs INSIDE the posting transaction. The locks taken by
+        // Sales-Post on the header, the lines, and the related ledger entries stay held
+        // for the entire round trip to the WMS.
+        //
+        // When the WMS is SLOW: every other user posting a sales document queues behind
+        // these locks. One slow endpoint serialises the whole team's posting.
+        //
+        // When the WMS is DOWN: this call blocks until the HTTP timeout fires, then throws.
+        // The throw propagates out of the posting transaction and the entire post ROLLS BACK.
+        // The shipment physically left the warehouse, but there is now no posted document
+        // and nothing was staged, so there is nothing to retry and nothing to inspect.
+        Client.Post('https://wms.contoso.com/api/shipments', Content, Response);
+
+        // Even on a success that is not actually success: a network blip after the WMS
+        // committed but before BC saw the response leaves the two systems disagreeing,
+        // with no staged row recording that the notification was attempted.
+    end;
+}