feat(testing): OHIF Test Agent Skills (#5993)

AGENTS.md

@@ -176,6 +176,10 @@ Always prioritrize pub sub, by calling a services subscribe over useEffects as i
 ### Never modify core architecture
 Do not modify the core and always find a way to implement the solution via the extensions and modes, only modify core as a last resort if all other fail or there's an architectural constraint.
 
+## Skills
+
+The `ohif-test-agent` skill (Playwright E2E test guidance) lives at `.agents/skills/ohif-test-agent/`.
+
 ## Configuration
 
 ### Plugin Configuration