ci: clean up backend test processes on cancel [CI]

ci/verify-backend.sh

@@ -84,31 +84,19 @@ status=0
 # Each test module can spawn its own testhost. Run the whole command in a new
 # session and time out its process group, so orphaned testhosts cannot keep the
 # Woodpecker step and the shared cache lock alive.
-if ! command -v setsid >/dev/null 2>&1; then
-  echo "setsid is required to enforce the backend test timeout" >&2
+if ! command -v python3 >/dev/null 2>&1; then
+  echo "python3 is required to enforce the backend test timeout" >&2
   exit 2
 fi
 
 run_with_timeout() {
-  local seconds="$1" marker="$cache/test-timeout.marker" test_pid watcher_pid result=0
+  local seconds="$1"
   shift
-  rm -f "$marker"
-  (
-    cd "$src/backend"
-    setsid "$@" &
-    test_pid=$!
-    setsid bash -c 'sleep "$1"; : > "$2"; kill -TERM -- "-$3" 2>/dev/null || true' _ "$seconds" "$marker" "$test_pid" >/dev/null 2>&1 &
-    watcher_pid=$!
-    wait "$test_pid" || result=$?
-    if [[ -f "$marker" ]]; then
-      kill -KILL -- "-$test_pid" 2>/dev/null || true
-      result=124
-    fi
-    kill -TERM -- "-$watcher_pid" 2>/dev/null || true
-    wait "$watcher_pid" 2>/dev/null || true
-    rm -f "$marker"
-    return "$result"
-  )
+  # A Python supervisor creates the test's session directly and owns its PID.
+  # This avoids setsid(1) forking away from the PID tracked by the old shell
+  # watchdog, which could leave testhosts alive (and holding the cache lock)
+  # after Woodpecker canceled the step.
+  (cd "$src/backend" && python3 "$root/ci/run-with-timeout.py" "$seconds" "$@")
 }
 
 # Ignore exit 8 from other assemblies with no matching tests; both suites have a hard wall-clock cap.