ci: remove unused canvasUserMessage type to fix lint on staging

internal/handlers/a2a_proxy_helpers.go:412 had an unused struct that
causes golangci-lint `unused` failure on every PR targeting staging.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workspace-server/internal/handlers/a2a_proxy_helpers.go

@@ -407,15 +407,6 @@ func validateCallerToken(ctx context.Context, c *gin.Context, callerID string) e
 // matching (the wsauth errors are typed for the invalid case).
 var errInvalidCallerToken = errors.New("missing caller auth token")
 
-// canvasUserMessage holds the extracted user message extracted from an
-// A2A canvas request body for broadcasting to other sessions.
-type canvasUserMessage struct {
-	Message   string                               `json:"message,omitempty"`
-	Parts     []map[string]interface{}              `json:"parts,omitempty"`
-	MessageID string                               `json:"messageId,omitempty"`
-	Attachments []map[string]interface{}            `json:"attachments,omitempty"`
-}
-
 // extractCanvasUserMessage parses an A2A JSON-RPC request body and extracts
 // the user-authored text and attachments from a canvas-initiated message/send.
 // Returns nil when the body is not a canvas user message (empty, malformed,

workspace-server/internal/handlers/discovery.go

@@ -348,6 +348,10 @@ func queryPeerMaps(query string, args ...interface{}) ([]map[string]interface{},
 
 		result = append(result, peer)
 	}
+	if err := rows.Err(); err != nil {
+		log.Printf("queryPeerMaps rows iteration error: %v", err)
+		return nil, err
+	}
 	return result, nil
 }