chore: Update to a2a-tck 0.3.0.beta (#262)

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Author: fjuma

.github/workflows/run-tck.yml

@@ -12,7 +12,7 @@ on:
 
 env:
   # Tag of the TCK
-  TCK_VERSION: 0.3.0.alpha
+  TCK_VERSION: 0.3.0.beta
   # Tells uv to not need a venv, and instead use system
   UV_SYSTEM_PYTHON: 1
   # SUT_JSONRPC_URL to use for the TCK and the server agent