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/accept-async-work-instead-of-synchronous-wait-loops.bad.al

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+// Anti-pattern: the inbound handler BLOCKS the request thread, Sleep-polling an external
+// service until it completes. The caller's connection is held open for the whole wait,
+// and concurrent requests pile up on pinned threads.
+
+codeunit 50123 "Inbound Intake Bad"
+{
+    // Called on the request path. It does not return until the remote work is done,
+    // so its runtime is entirely dictated by a system BC does not control.
+    procedure Accept(Payload: Text): Text
+    var
+        Client: HttpClient;
+        Response: HttpResponseMessage;
+        JobId: Text;
+        Done: Boolean;
+    begin
+        JobId := StartRemoteJob(Client, Payload);
+
+        // BAD: Sleep inside a loop on the request thread. This single request now holds
+        // its thread and session slot for the full duration of the remote job.
+        repeat
+            // When the downstream is SLOW: this blocks for seconds or minutes. The caller's
+            // HTTP connection times out long before the loop ends, and the work it kicked
+            // off is orphaned with no staged row recording it.
+            Sleep(2000);
+
+            // When the downstream is DOWN: this Get blocks until its own timeout, every
+            // iteration, making a slow failure even slower.
+            Client.Get(StrSubstNo('https://svc.contoso.com/jobs/%1', JobId), Response);
+            Done := IsComplete(Response);
+        until Done;
+
+        // Under load: each in-flight request pins a thread here. A handful of slow calls
+        // exhaust the request slots and BC starts rejecting healthy callers too. One slow
+        // dependency becomes a site-wide outage.
+        exit('completed'); // by now the original caller has almost certainly timed out
+    end;
+}