Add AGENTS.md file for test server

Author: Quinn-With-Two-Ns

temporal-test-server/AGENTS.md

@@ -0,0 +1,28 @@
+# temporal-test-server Contributor Guide
+
+This module contains an in-memory implementation of the Temporal service that is used for testing. It is typically consumed indirectly via `TestWorkflowEnvironment` from the **temporal-testing** module. The module can also be compiled into a standalone executable for use by tests written in other languages.
+
+## Directory layout
+- `src/main/java` – Java implementation of the test service. The main entry point is `io.temporal.testserver.TestServer`.
+- `src/main/proto` – Protobuf definitions for the service plus a `Makefile` and `buf.yaml` for linting and code generation. Generated sources live under `build/generated`.
+- `src/main/resources/META-INF/native-image` – Configuration used when building a GraalVM native image.
+- `src/test/java` – Unit and functional tests using `SDKTestWorkflowRule`.
+- `src/test/resources` – Test utilities such as logging configuration.
+
+## Typical tasks
+Run these commands from the repository root.
+
+### Format and build
+```bash
+./gradlew --offline spotlessApply
+./gradlew :temporal-test-server:test
+./gradlew :temporal-test-server:build
+```
+
+
+## Notes for contributors
+- Do not depend on this module directly from applications. Instead depend on `temporal-testing`.
+- The code under `internal` packages is not part of the public API and may be changed freely.
+- Java 8 compatibility is required.
+- Follow repository wide guidelines in the root `AGENTS.md` for commit style and verification (`spotlessCheck`, running tests, etc.).
+- Testing should be done with the workflow service stub in general not the WorkflowClient