docs: add AGENTS.md contributor-safe guidance

Author: timothytlewis

AGENTS.md

@@ -0,0 +1,25 @@
+# AGENTS: brewkit
+
+Public repository for package build/test/audit workflows.
+
+## Core Commands
+
+- `bin/bk build <pkg>`
+- `bin/bk test <pkg>`
+- `bin/bk audit <pkg>`
+- `deno test --allow-env --allow-net --ignore=.data`
+
+## Always Do
+
+- Keep package build behavior deterministic.
+- Test and audit packages touched by the change.
+
+## Ask First
+
+- Changes to CI action contracts.
+- Changes that alter bottle/build artifact naming or layout.
+
+## Never Do
+
+- Never skip `bk audit` for modified package workflows.
+- Never embed internal-only operational details in public docs.