fix(action): allow forward sync from trailer commits

tests/unit/action.bats

@@ -0,0 +1,17 @@
+#!/usr/bin/env bats
+# tests/unit/action.bats — Composite action regression tests
+
+setup() {
+  JOSH_SYNC_ROOT="$(cd "$BATS_TEST_DIRNAME/../.." && pwd)"
+  ACTION_FILE="${JOSH_SYNC_ROOT}/action.yml"
+}
+
+@test "forward sync is not globally skipped when HEAD has the sync trailer" {
+  ! grep -q "Loop guard (forward)" "$ACTION_FILE"
+  ! grep -q "HEAD commit has sync trailer" "$ACTION_FILE"
+  ! grep -q "steps.guard.outputs.skip" "$ACTION_FILE"
+}
+
+@test "composite action still invokes the josh-sync CLI" {
+  grep -q "josh-sync sync" "$ACTION_FILE"
+}