Establish watch relay contracts and platform package wiring

Adapters/WatchBridge/Sources/Watch/WatchCommandPayload.swift

@@ -0,0 +1,10 @@
+import RemoteCore
+import WatchBridgeCommon
+
+/// Pure outgoing container construction: does not activate WCSession, grant a
+/// session, queue a command, or transmit it. Live delivery belongs to B.
+public enum WatchCommandPayload {
+    public static func container(for envelope: CommandEnvelope) throws -> RelayContainer {
+        try RelayContainer(kind: .command, value: envelope)
+    }
+}