CAMEL-22325: Add AGENTS.md section to enforce Awaitility over Thread.sleep (#22371)

Signed-off-by: Andrea Cosentino <ancosen@gmail.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: oscerd

AGENTS.md

@@ -76,6 +76,29 @@ When creating a PR, **always identify and request reviews** from the most releva
 - All code must pass formatting checks (`mvn formatter:format impsort:sort`) before pushing.
 - All generated files must be regenerated and committed (CI checks for uncommitted changes).
 
+### Asynchronous Testing: Use Awaitility Instead of Thread.sleep
+
+Do **NOT** use `Thread.sleep()` in test code. It leads to flaky, slow, and non-deterministic tests.
+Use the [Awaitility](https://github.com/awaitility/awaitility) library instead, which is already
+available as a test dependency in the project.
+
+**Example — waiting for a route to be registered:**
+
+```java
+import static org.awaitility.Awaitility.await;
+
+await().atMost(20, TimeUnit.SECONDS)
+       .untilAsserted(() -> assertEquals(1, context.getRoutes().size()));
+```
+
+**Rules:**
+
+- New test code MUST NOT introduce `Thread.sleep()` calls.
+- When modifying existing test code that contains `Thread.sleep()`, migrate it to Awaitility.
+- Always set an explicit `atMost` timeout to avoid hanging builds.
+- Use `untilAsserted` or `until` with a clear predicate — do not replace a sleep with a
+  busy-wait loop.
+
 ### Issue Investigation (Before Implementation)
 
 Before implementing a fix for a JIRA issue, **thoroughly investigate** the issue's validity and context.