feat(#919): adopt session.usage WS push event for real-time context & compression updates (#927)

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/data/ws/EventParser.kt

@@ -167,6 +167,10 @@ object EventParser {
                 WsEvent.SessionUpdated(payload)
             }
 
+            "session.usage" -> {
+                WsEvent.SessionUsage(payload, sessionId)
+            }
+
             "reaction" -> {
                 val kind = payload?.get("kind") as? String ?: ""
                 WsEvent.ReactionEvent(kind)

app/src/main/java/com/m57/hermescontrol/data/ws/WsEvent.kt

@@ -161,6 +161,16 @@ sealed class WsEvent {
         val data: Map<String, Any?>?,
     ) : WsEvent()
 
+    /**
+     * Live token & compression usage snapshot emitted during a turn (issue #919).
+     * Carried in `session.usage` push events (`tui_gateway/server.py` `_start_usage_ticker`).
+     * Payload: `{ "usage": { "compressions": Int, "context_used": Long, "context_max": Long, ... } }`
+     */
+    data class SessionUsage(
+        val data: Map<String, Any?>?,
+        val sessionId: String? = null,
+    ) : WsEvent()
+
     // ── RPC responses ────────────────────────────────────────────────────
 
     data class RpcResult(