nixos: disable moq-native websocket fallback for wt-publish

evolution/proposals/ECP-0063-cloudflare-moq-webtransport.md

@@ -59,6 +59,7 @@ newer draft implementations.
 
 Implementation choice:
 - Cloudflare's relay preview currently does **not** support `ANNOUNCE` (namespace-style publishing). `ec-node wt-publish` uses the `moq-lite` publish model via `moq-native` and `moq-mux` (fMP4 ingestion) for Cloudflare relay compatibility.
+- On NixOS deployments, we disable `moq-native`'s WebSocket fallback (`MOQ_CLIENT_WEBSOCKET_ENABLED=false`) to ensure WebTransport (QUIC) is used. This avoids the WebSocket path occasionally "winning" the race and then failing MoQ negotiation against the Cloudflare relay, causing rapid reconnect loops.
 
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nix/modules/ec-node.nix

@@ -80,6 +80,9 @@ in
       type = lib.types.attrsOf lib.types.str;
       default = {
         RUST_LOG = "info";
+        # Cloudflare's relay is WebTransport-first; moq-native's WebSocket fallback can "win"
+        # the race and then fail MoQ negotiation, causing a tight reconnect loop.
+        MOQ_CLIENT_WEBSOCKET_ENABLED = "false";
       };
       description = "Environment variables for the publisher services.";
     };