Function restore_cache_dir

tests/test_mcp.c:108–114

}

static void restore_cache_dir(const char *saved_copy) {
    if (saved_copy) {
        cbm_setenv("CBM_CACHE_DIR", saved_copy, 1);
    } else {
        cbm_unsetenv("CBM_CACHE_DIR");
    }
}

static void cleanup_project_db(const char *cache, const char *project) {
    if (!cache || !project) {