docs: add AGENTS.md contributor-safe guidance

Author: timothytlewis

AGENTS.md

@@ -0,0 +1,24 @@
+# AGENTS: setup
+
+Public repository for installer scripts and GitHub Action setup.
+
+## Core Commands
+
+- `npm install`
+- `npm run dist`
+- `sh ./installer.sh --help`
+
+## Always Do
+
+- Keep installer behavior explicit across macOS, Linux, and Windows.
+- Preserve action input/output contract stability.
+
+## Ask First
+
+- Any change to default install paths or update behavior.
+- Any action permission or deployment behavior change.
+
+## Never Do
+
+- Never remove installer safety checks.
+- Never introduce hidden network side effects without documentation.