test: document latest DXVK release resolution

tests/common_test.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+source "$REPO_ROOT/scripts/common.sh"
+
+expected_tag="latest"
+actual_tag="$(dxvk_tag_for_variant stable)"
+
+if [[ "$actual_tag" != "$expected_tag" ]]; then
+  printf 'expected stable DXVK tag %s, got %s\n' "$expected_tag" "$actual_tag" >&2
+  exit 1
+fi
+
+printf 'stable DXVK tag resolves dynamically as %s\n' "$actual_tag"