Fix memory leak in resolve_store + Windows setenv build error

- resolve_store: verify project exists in database after opening;
  close store immediately if project is absent (prevents SQLite
  connection leak when querying deleted/empty projects)
- test_userconfig.c: use cbm_setenv/cbm_unsetenv instead of raw
  POSIX setenv/unsetenv (fixes Windows build)

Author: DeusData

src/mcp/mcp.c

@@ -653,9 +653,17 @@ static cbm_store_t *resolve_store(cbm_mcp_server_t *srv, const char *project) {
     project_db_path(project, path, sizeof(path));
     srv->store = cbm_store_open_path_query(path);
     if (srv->store) {
-        /* Only update ownership and cached project name on successful open.
-         * When the file is absent, store is NULL and current_project retains
-         * its previous value so the next call correctly retries the open. */
+        /* Verify the project actually exists in this database.
+         * A .db file may exist but be empty (e.g., after delete_project on
+         * Linux where unlink defers actual removal). Opening an empty/deleted
+         * store without closing it leaks the SQLite connection. */
+        cbm_project_t proj_verify = {0};
+        if (cbm_store_get_project(srv->store, project, &proj_verify) != CBM_STORE_OK) {
+            cbm_store_close(srv->store);
+            srv->store = NULL;
+            return NULL;
+        }
+        cbm_project_free_fields(&proj_verify);
         srv->owns_store = true;
         free(srv->current_project);
         srv->current_project = heap_strdup(project);

tests/test_integration.c

@@ -410,7 +410,6 @@ TEST(integ_mcp_delete_project) {
     snprintf(args, sizeof(args), "{\"label\":\"Function\",\"project\":\"%s\"}", g_project);
     resp = call_tool("search_graph", args);
     ASSERT_NOT_NULL(resp);
-    /* Guard returns "not indexed" error or "no project loaded"; either is correct */
     ASSERT_TRUE(strstr(resp, "total") != NULL || strstr(resp, "not indexed") != NULL ||
                 strstr(resp, "no project loaded") != NULL);
     free(resp);

tests/test_userconfig.c

@@ -71,9 +71,9 @@ TEST(userconfig_global_via_env) {
         0);
 
     /* Set env var, load, restore */
-    setenv("XDG_CONFIG_HOME", xdg_dir, 1);
+    cbm_setenv("XDG_CONFIG_HOME", xdg_dir, 1);
     cbm_userconfig_t *cfg = cbm_userconfig_load(NULL); /* no project dir */
-    unsetenv("XDG_CONFIG_HOME");
+    cbm_unsetenv("XDG_CONFIG_HOME");
 
     ASSERT_NOT_NULL(cfg);
     ASSERT_EQ(cbm_userconfig_lookup(cfg, ".twig"), CBM_LANG_HTML);
@@ -110,9 +110,9 @@ TEST(userconfig_project_wins_over_global) {
         write_json(proj_path, "{\"extra_extensions\":{\".xyz\":\"rust\"}}"),
         0);
 
-    setenv("XDG_CONFIG_HOME", xdg_dir, 1);
+    cbm_setenv("XDG_CONFIG_HOME", xdg_dir, 1);
     cbm_userconfig_t *cfg = cbm_userconfig_load(proj_dir);
-    unsetenv("XDG_CONFIG_HOME");
+    cbm_unsetenv("XDG_CONFIG_HOME");
 
     ASSERT_NOT_NULL(cfg);
     /* Project definition (rust) must win */