Clarify integration test synchronization (#21414)

Signed-off-by: Wouter Born <github@maindrain.net>

Author: wborn

AGENTS.md

@@ -252,6 +252,8 @@ When modifying existing behavior, inspect existing tests first and extend them r
 - Integration tests are located in the `itests/` directory.
 - Use bndrun configurations to define realistic OSGi runtime environments.
 - For lifecycle-sensitive changes, consider activation, deactivation, reactivation, service arrival/removal, and different installation orders where relevant.
+- In bnd-based integration tests, do not infer a service-availability race merely from a direct `getService(...)` call during test setup. Services supplied by the resolved runtime are normally available before the tests execute; use polling only when the specific service can actually arrive asynchronously after test execution has started.
+- When an integration test modifies a provider tracked by an `AbstractRegistry`-based registry, ensure asynchronous registry activation has completed before modifying the provider. Use `waitForCompletedAsyncActivationTasks()` when available, before adding, updating, or removing provider elements.
 
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