feat(ha-repl-hardening): add StateReport to RequestReply capnp schema (task 1.1)

Add StateReport struct {appliedLsn, configTag} as stateReportMsg @15
variant in RequestReply.data union. Standby populates this in heartbeat
replies so the primary can track per-standby convergence.

capnpc-c 1.0.1 has a bug with inline :group inside codecgen unions;
workaround uses named outer struct (wire-equivalent). typemap.h
extended with state_report_t and union member for C codec access.

.kiro/specs/ha-repl-hardening/tasks.md

@@ -9,7 +9,7 @@
 ---
 
 - [ ] 1. Foundation: Schema changes and state tracking fields
-- [ ] 1.1 Add `stateReport` group to `RequestReply.data` union in controller.capnp
+- [x] 1.1 Add `stateReport` group to `RequestReply.data` union in controller.capnp
   - Add `appliedLsn :UInt64 @15` and `configTag :UInt64 @16` fields inside a `stateReport :group` variant
   - Regenerate capnp bindings; verify compilation succeeds
   - Existing decode paths and opcode dispatch unaffected

src/include/typemap.h

@@ -186,6 +186,12 @@ typedef struct {
     uint64_t peer_last_log_lsn;
 } request_vote_reply_t;
 
+/* Heartbeat reply state report — carries standby's applied_lsn and config_tag */
+typedef struct {
+    uint64_t applied_lsn;
+    uint64_t config_tag;
+} state_report_t;
+
 typedef struct {
     uint64_t seq;
     uint32_t opcode;
@@ -201,6 +207,7 @@ typedef struct {
         upgrade_config_reply_t*    upgradeconfigreplymsg;
         ctrl_hello_reply_t*        ctrlhelloreplymsg;
         request_vote_reply_t*      requestvotereplymsg;
+        state_report_t*            state_report;
     } data;
     /* Req 7: standby redirect fields — populated when status == XCE_ERR_STANDBY */
     char    *redirect_host;

src/schema/controller.capnp

@@ -559,6 +559,7 @@ struct RequestReply $C.mapname("xce_reply_t"){
     upgradeconfigreplymsg    @10: UpgradeConfigReply;
     ctrlhelloreplymsg        @13: CtrlHelloReply;
     requestvotereplymsg      @14: RequestVoteReply;
+    stateReportMsg      @15: StateReport $C.mapname("state_report"); # heartbeat reply: standby state
   }
 
   redirectHost @11: Text   $C.mapname("redirect_host");
@@ -782,6 +783,13 @@ struct ReplEnvelope $C.mapname("capnp_repl_envelope_t") {
 
 # ── HA election and replication message structs (Task 1.1) ───────────
 
+# Heartbeat reply state report — standby piggybacks its replication state
+# onto every OPCode_nop reply so the primary can drive convergence decisions.
+struct StateReport $C.mapname("state_report_t") {
+  appliedLsn @0 :UInt64 $C.mapname("applied_lsn");   # standby's last applied WAL LSN
+  configTag  @1 :UInt64 $C.mapname("config_tag");    # standby's current config version tag
+}
+
 struct RequestVoteRequest $C.mapname("request_vote_req_t") {
   term        @0 :UInt64 $C.mapname("term");
   candidateId @1 :Text   $C.mapname("candidate_id");