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/deduplicate-inbound-messages-with-an-idempotency-check.bad.al

@@ -0,0 +1,33 @@
+// Anti-pattern: insert on every call with no idempotency check, keyed on a brand-new GUID.
+// A retried or re-fetched delivery is processed again as a fresh message, so a duplicating
+// source produces duplicate documents and double-applied side effects.
+
+codeunit 50142 "Inbound Dedup Bad"
+{
+    procedure Stage(ExternalRef: Text[100]; MsgType: Code[40]; Payload: Text): Guid
+    var
+        IntegrationMessage: Record "Integration Message";
+    begin
+        // BAD: no SetRange on External Reference + Type, no Get, no lookup of any kind.
+        // The source system's stable id is captured on the row but never used to detect a repeat.
+        IntegrationMessage.Init();
+
+        // BAD: the only "identity" is a fresh GUID. If anyone later "dedups" on Message ID,
+        // it can never match, because every insert mints a new one. This is the illusion of a
+        // dedup key that can never actually fire.
+        IntegrationMessage."Message ID" := CreateGuid();
+
+        IntegrationMessage.Direction := IntegrationMessage.Direction::Inbound;
+        IntegrationMessage."External Reference" := ExternalRef;
+        IntegrationMessage.Type := MsgType;
+        IntegrationMessage.Status := IntegrationMessage.Status::New;
+        IntegrationMessage.SetRequest(Payload);
+
+        // When the source RETRIES (a webhook that did not see our ack, a restart re-send, an
+        // overlapping poll window): this runs again with the same ExternalRef and stages a
+        // second message. Downstream it becomes a second sales order and a second posting.
+        // The duplicate volume scales with how aggressively the source retries.
+        IntegrationMessage.Insert(true);
+        exit(IntegrationMessage."Message ID");
+    end;
+}