feat(libxce-failover): reconnect/rejoin hook — public setter + post-reconnect invocation before resume (task 4.1)

src/lib/client.c

@@ -76,6 +76,27 @@ int xcecli_set_handler(xcecli_ctx_t c, xce_request_handler_t handler,
     return xce_ctx_set_handler(&(ctx->ctx), handler, args);
 }
 
+/*
+ * xcecli_set_reconnect_handler (task 4.1) — register the consumer rejoin hook
+ * the failover loop invokes after a transparent reconnect, before resuming the
+ * interrupted op. A NULL cb clears any previously registered hook (back to the
+ * pure-client no-op path). Stores cb+arg on the per-ctx failover state.
+ */
+int xcecli_set_reconnect_handler(xcecli_ctx_t c, xcecli_reconnect_cb cb,
+                                 void* arg)
+{
+    api_ctx_t* ctx = (api_ctx_t*)c;
+
+    if (c == NULL) {
+        return -EINVAL;
+    }
+
+    ctx->failover.rejoin_cb  = cb;
+    ctx->failover.rejoin_arg = arg;
+
+    return 0;
+}
+
 int xcecli_wakeup(xcecli_ctx_t c, int status)
 {
     api_ctx_t* ctx = (api_ctx_t*)c;