feat(libxce-failover): foundation — per-ctx failover state, redirect-hint fields, remove orphaned retry primitive (task 1.1)

src/include/xcectx.h

@@ -2,6 +2,9 @@
 
 #define _XCECTX_H_ 1
 
+#include <stdint.h>
+
+#include "config.h" /* XCE_MAXHOSTNAME_LEN */
 #include "netio.h"
 #include "request.h"
 #include "vtaskmgr.h"
@@ -28,6 +31,13 @@ typedef struct {
     cbuf_t                wbuf;
     dataset_t*            dataset;
 
+    /* Redirect-hint address captured from the last redirect reply by
+     * handle_reply() (which only sees xce_ctx_t) and read by the failover
+     * rotator on the next retry. Empty host ("") means no hint. Advisory only;
+     * correctness never depends on it. */
+    char     redirect_hint_host[XCE_MAXHOSTNAME_LEN];
+    uint16_t redirect_hint_port;
+
     struct {
         union {
             char*              debugmsg;