Improve AGENTS workflow notes (#747)

* clarify workflow instructions

* agents feedback

AGENTS.md

@@ -0,0 +1,49 @@
+# AGENTS Instructions
+
+This repository is a Yarn v4 monorepo with several workspaces:
+- `app` – mobile app (@selfxyz/mobile-app)
+- `circuits` – zk-SNARK circuits (@selfxyz/circuits)
+- `common` – shared utilities (@selfxyz/common)
+- `contracts` – solidity contracts (@selfxyz/contracts)
+- `sdk/core` – core TypeScript SDK (@selfxyz/core)
+- `sdk/qrcode` – qrcode SDK (@selfxyz/qrcode)
+
+## Workflow
+
+### Setup
+- Run `yarn install` once before running any other commands. This installs root dependencies and sets up husky hooks.
+
+### Commit Checks
+Before committing, run the following commands:
+
+```bash
+# Lint all packages in parallel
+yarn lint
+
+# Build all workspaces except `contracts`
+yarn build
+
+# Compile Solidity contracts (may occasionally throw a Hardhat config error)
+yarn workspace @selfxyz/contracts build
+
+# Run type-checking across the repo
+yarn types
+```
+
+### Tests
+- Run unit tests where available:
+  - `yarn workspace @selfxyz/common test`
+  - `yarn workspace @selfxyz/circuits test`  # may fail if OpenSSL algorithms are missing
+  - `yarn workspace @selfxyz/mobile-app test`
+  - Tests for `@selfxyz/contracts` are currently disabled in CI and may be skipped.
+
+### Formatting
+- Use Prettier configuration from `.prettierrc` files.
+- Follow `.editorconfig` for line endings and indentation.
+
+### Commit Guidelines
+- Write short, imperative commit messages (e.g. `Fix address validation`).
+- The pull request body should summarize the changes and mention test results.
+
+## Scope
+These instructions apply to the entire repository unless overridden by a nested `AGENTS.md`.