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/api/expose-bc-entities-as-api-pages-for-external-agents.good.al

@@ -0,0 +1,44 @@
+// Best practice: a top-level API page whose entity names and version form a
+// stable contract for an external agent, shaped read-only because the agent's
+// workflow only needs to read. Demonstration-only; not a deployed object.
+
+page 50120 "Agent Customer API"
+{
+    // Only top-level PageType = API pages surface as agent tools. A ListPart or
+    // CardPart here would be silently unreachable by the agent.
+    PageType = API;
+    SourceTable = Customer;
+
+    // These five properties are the contract. They are fixed literals, so the
+    // route and the tool names the agent binds to never shift under it.
+    APIPublisher = 'contoso';
+    APIGroup = 'sales';
+    APIVersion = 'v1.0';
+    // EntityName and EntitySetName become the singular/plural tool names. They
+    // use the agent's domain vocabulary, not the table's internal captions.
+    EntityName = 'customer';
+    EntitySetName = 'customers';
+
+    // The agent only reads, so the whole surface is locked to read. A read tool
+    // can never mutate, no matter what the prompt asks for.
+    Editable = false;
+    InsertAllowed = false;
+    ModifyAllowed = false;
+    DeleteAllowed = false;
+
+    layout
+    {
+        area(Content)
+        {
+            repeater(Group)
+            {
+                // A narrow, deliberately chosen field set: exactly what the
+                // agent reasons over, named for the agent, nothing more.
+                field(number; Rec."No.") { Caption = 'number'; }
+                field(displayName; Rec.Name) { Caption = 'displayName'; }
+                field(city; Rec.City) { Caption = 'city'; }
+                field(balanceDue; Rec."Balance Due (LCY)") { Caption = 'balanceDue'; }
+            }
+        }
+    }
+}