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/set-instructions-as-secrettext.md

@@ -0,0 +1,26 @@
+---
+bc-version: [27..]
+domain: agents
+keywords: [setinstructions, secrettext, instructions, per-instance, resource]
+technologies: [al]
+countries: [w1]
+application-area: [all]
+---
+
+# Set agent instructions as SecretText on the instance
+
+## Description
+
+Instructions are instance data, not an enum caption. `Agent.SetInstructions` takes `SecretText` so the payload is not logged or copied as ordinary text. A Label or plaintext Text on the agent type is the wrong store: it leaks into telemetry-friendly strings and cannot vary per instance or company.
+
+## Best Practice
+
+Load instruction text from a resource or builder into a `SecretText` variable and call `Agent.SetInstructions(AgentUserSecurityId, Instructions)` after `Create`. Keep one instruction document per instance.
+
+See sample: `set-instructions-as-secrettext.good.al`.
+
+## Anti Pattern
+
+Passing a `Label` or `Text` to `SetInstructions`, storing instructions in a setup Text field without wrapping as `SecretText`, or putting the prompt only in a code comment. Detection signal: `SetInstructions` with a non-`SecretText` argument, or no `SetInstructions` after `Create`.
+
+See sample: `set-instructions-as-secrettext.bad.al`.