ci: experiment with cancel-in-progress on the test pipeline

Assisted-by: GLM 5.3 Flash

.gitea/workflows/test.yml

@@ -30,6 +30,13 @@ env:
   GOFLAGS: -p=1
   GOMAXPROCS: "2"
 
+# A superseded run of the same ref is cancelled instead of queueing behind one
+# that no longer matters. Unverified on this Gitea: this block is the experiment
+# from the roadmap, push twice in a row and watch whether the first run cancels.
+concurrency:
+  group: ${{ gitea.workflow }}-${{ gitea.ref }}
+  cancel-in-progress: true
+
 jobs:
   test:
     runs-on: fedora