Add community guidance and review support for Business Central agents (#137)

* feat(community/agents): add AL agent quality guidance

- add 20 agent knowledge rules with good and bad AL samples
- clarify setup dialog shape, temporary persistence, permissions, profiles, instructions, capability registration, and interface wiring
- add the community-owned AL agents review skill
- make review fixture discovery layer-aware with custom, community, and Microsoft precedence
- document layer-aware evaluation behavior

* fix(community/agents): align setup and permission samples

- mark agent setup pages as non-extensible where required
- narrow the agent profile by hiding an unrelated sales-order field
- define a dedicated read-only permission set for the sales review agent
- assign AL-defined permission sets with system scope and the owning app ID
- clarify the permission scope guidance for default access controls

* Address agent review feedback

community/knowledge/agents/agent-setup-page-is-configuration-dialog.bad.al

@@ -0,0 +1,19 @@
+page 50100 "Sales Review Agent Setup"
+{
+    PageType = Card;
+    Caption = 'Set up Sales Review Agent';
+    SourceTable = "Sales Review Agent Setup";
+
+    layout
+    {
+        area(Content)
+        {
+            field(ReviewThreshold; Rec."Review Threshold")
+            {
+                ApplicationArea = All;
+                Caption = 'Review Threshold';
+                ToolTip = 'Specifies the threshold used when the agent requests a review.';
+            }
+        }
+    }
+}