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.md

@@ -0,0 +1,30 @@
+---
+bc-version: [27..]
+domain: agents
+keywords: [copilot-capability, registercapability, install, feature-switch, enumextension]
+technologies: [al]
+countries: [w1]
+application-area: [all]
+---
+
+# Register a Copilot capability for the agent on install
+
+## Description
+
+Each agent type needs a `Copilot Capability` enum value that the factory links as the feature switch and billing surface. The capability is invisible on Copilot and agent capabilities until an install codeunit calls `RegisterCapability` when it is not already registered. Unique ordinals matter across installed apps. Models often extend `Agent Metadata Provider` and never register the capability.
+
+## Best Practice
+
+Extend `Copilot Capability` with a unique value. In `OnInstallAppPerDatabase`, call `Copilot Capability.IsCapabilityRegistered` and, if false, `RegisterCapability` with availability, billing type, and a learn-more URL. Point `IAgentFactory` at that capability.
+
+See sample: `register-copilot-capability-for-the-agent.good.al`.
+
+## Anti Pattern
+
+Shipping the agent enum without a `Copilot Capability` value, or adding the enum but never calling `RegisterCapability`. Duplicate ordinals across extensions also collide. Detection signal: agent metadata provider with no matching capability registration in an install codeunit.
+
+See sample: `register-copilot-capability-for-the-agent.bad.al`.
+
+## See also
+
+`wire-all-three-agent-interfaces.md` covers registration of the provider implementation that references this capability.