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

community/knowledge/agents/agent-permissions-intersect-with-assigner.bad.al

@@ -0,0 +1,11 @@
+permissionset 50100 "SALES REVIEW AGENT"
+{
+    Assignable = true;
+    Permissions =
+        tabledata "Sales Header" = RIM,
+        tabledata Customer = R,
+        tabledata User = RIMD,
+        tabledata "Access Control" = RIMD,
+        page "Sales Order" = X,
+        page "User Card" = X;
+}