feat(nat): make NAT prediction deployment-configurable (#372)

* Make NAT prediction deployment-configurable

* Ignore optional predicted candidate rejection

docs/README.md

@@ -45,8 +45,8 @@ ordinary implementation and UI detail.
   owned media adaptation.
 - [ADR-0008](./adr/0008-window-scoped-audio-capture.md): Browser/native window
   audio boundary.
-- [ADR-0009](./adr/0009-connection-local-nat-prediction-experiment.md): opt-in
-  connection-local NAT candidate experiment.
+- [ADR-0009](./adr/0009-optional-nat-prediction.md): optional connection-local
+  NAT prediction.
 
 ## Evidence