chore: Run TCK on 0.3.x branch too, and use latest TCK (a2aproject#421)

Author: kabir

.github/workflows/run-tck.yml

@@ -5,14 +5,17 @@ on:
   push:
     branches:
       - main
+      - 0.3.x
   pull_request:
     branches:
       - main
+      - 0.3.x
   workflow_dispatch:
 
 env:
+  # TODO once we have the TCK for 0.4.0 we will need to look at the branch to decide which TCK version to run.
   # Tag of the TCK
-  TCK_VERSION: 0.3.0.beta2
+  TCK_VERSION: 0.3.0.beta3
   # 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