feat: add validation to ingest gateway

HTTP and WebSocket handlers now validate events before publishing.
Returns detailed error info on validation failures.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/ingest-gateway/main.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"os"
 
+	"agentmon/internal/event"
 	"agentmon/internal/httpx"
 	qnats "agentmon/internal/queue/nats"
 
@@ -45,11 +46,28 @@ func main() {
 
 		accepted := 0
 		rejected := 0
+		var errors []map[string]any
 		for _, raw := range events {
 			if len(raw) == 0 {
 				rejected++
 				continue
 			}
+
+			var m map[string]any
+			if err := json.Unmarshal(raw, &m); err != nil {
+				rejected++
+				errors = append(errors, map[string]any{"error": "invalid_json"})
+				continue
+			}
+
+			if err := event.Validate(m); err != nil {
+				rejected++
+				if ve, ok := err.(event.ValidationError); ok {
+					errors = append(errors, map[string]any{"error": "validation_failed", "field": ve.Field, "message": ve.Message})
+				}
+				continue
+			}
+
 			if err := pub.Publish(r.Context(), raw); err != nil {
 				rejected++
 				continue
@@ -57,7 +75,11 @@ func main() {
 			accepted++
 		}
 
-		httpx.WriteJSON(w, http.StatusAccepted, map[string]any{"accepted": accepted, "rejected": rejected})
+		resp := map[string]any{"accepted": accepted, "rejected": rejected}
+		if len(errors) > 0 {
+			resp["errors"] = errors
+		}
+		httpx.WriteJSON(w, http.StatusAccepted, resp)
 	})
 
 	r.Get("/v1/ws", wsHandler(pub))
@@ -84,18 +106,26 @@ func wsHandler(pub *qnats.Publisher) http.HandlerFunc {
 				return
 			}
 
-			var v map[string]any
+			var m map[string]any
-			if err := json.Unmarshal(msg, &v); err != nil {
+			if err := json.Unmarshal(msg, &m); err != nil {
 				_ = conn.WriteJSON(map[string]any{"error": "invalid_json"})
 				continue
 			}
 
+			if err := event.Validate(m); err != nil {
+				if ve, ok := err.(event.ValidationError); ok {
+					_ = conn.WriteJSON(map[string]any{"error": "validation_failed", "field": ve.Field, "message": ve.Message})
+				} else {
+					_ = conn.WriteJSON(map[string]any{"error": "validation_failed"})
+				}
+				continue
+			}
+
 			if err := pub.Publish(r.Context(), msg); err != nil {
 				_ = conn.WriteJSON(map[string]any{"error": "publish_failed"})
 				continue
 			}
 
-			_ = v
 			_ = conn.WriteJSON(map[string]any{"ack": map[string]any{"up_to_seq": nil}})
 		}
 	}