fix: client-cancelled GET /v0/servers returns 499 without error log (#1335)

Maps context.Canceled from ListServers to 499 and skips the error-level log on client disconnect.

Merged as-is per maintainer decision; known follow-up tracked in #1337 (500-path error-detail leak + WriteHeader claim correction + nits).

internal/api/handlers/v0/list_errors.go

@@ -0,0 +1,21 @@
+package v0
+
+import (
+	"context"
+	"errors"
+	"log"
+
+	"github.com/danielgtaylor/huma/v2"
+)
+
+// ListServersError maps ListServers failures; client disconnects must not log as 500s.
+func ListServersError(ctx context.Context, err error) error {
+	if err == nil {
+		return nil
+	}
+	if errors.Is(err, context.Canceled) || errors.Is(ctx.Err(), context.Canceled) {
+		return huma.NewError(499, "Client closed request", err)
+	}
+	log.Printf("list servers failed: %v", err)
+	return huma.Error500InternalServerError("Failed to get registry list", err)
+}