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/register-copilot-capability-for-the-agent.bad.al

@@ -0,0 +1,21 @@
+enumextension 50100 "Sales Review Agent Metadata" extends "Agent Metadata Provider"
+{
+    value(50100; "Sales Review Agent")
+    {
+        Caption = 'Sales Review Agent';
+        Implementation = IAgentFactory = "Sales Review Agent Factory",
+                         IAgentMetadata = "Sales Review Agent Metadata",
+                         IAgentTaskExecution = "Sales Review Agent Task";
+    }
+}
+
+codeunit 50101 "Sales Review Agent Install"
+{
+    Subtype = Install;
+    Access = Internal;
+
+    trigger OnInstallAppPerDatabase()
+    begin
+        // Agent type exists, but no Copilot Capability value and no RegisterCapability.
+    end;
+}