feat(events): run notify side effects and ack on one fenced transaction

Shadow dry-runs the same handler then rolls back, writing only the intended digest.

Co-authored-by: Cursor <cursoragent@cursor.com>

cmd/events/main.go

@@ -11,9 +11,12 @@ import (
 	"syscall"
 	"time"
 
+	"chat-agent-system/internal/app/docnotify"
 	"chat-agent-system/internal/config"
 	"chat-agent-system/internal/db"
+	"chat-agent-system/internal/docgov"
 	"chat-agent-system/internal/events"
+	"chat-agent-system/internal/notification"
 
 	"github.com/jackc/pgx/v5/pgxpool"
 )
@@ -57,6 +60,10 @@ func main() {
 
 	owner := fmt.Sprintf("events-%d", os.Getpid())
 	disp := events.NewDispatcher(pool, cfg.Env, owner)
+	notify := notification.NewService(pool)
+	_ = disp.Register(events.ConsumerNotify, (&docnotify.EventConsumer{
+		Notify: notify, Docs: docgov.NewGovernanceEngine(pool), Env: cfg.Env,
+	}).HandleLease)
 	mux := http.NewServeMux()
 	mux.HandleFunc("GET /health", func(w http.ResponseWriter, _ *http.Request) {
 		writeJSON(w, http.StatusOK, map[string]any{"status": "ok", "env": cfg.Env, "owner": owner})