fix(ws): suppress deferred-API RPC error events for opt-in callers (#1265)

Co-authored-by: m57 <41645758+Hy4ri@users.noreply.github.com>

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

@@ -775,6 +775,7 @@ object HermesWsClient {
         val method: String,
         val deferred: CompletableDeferred<Any?>,
         var timeoutJob: Job? = null,
+        val suppressErrorEvent: Boolean = false,
     )
 
     /** Tracks in-flight [request] calls by their JSON-RPC id. */
@@ -794,11 +795,12 @@ object HermesWsClient {
         method: String,
         params: Map<String, Any> = emptyMap(),
         timeoutMs: Long = REQUEST_TIMEOUT_MS,
+        suppressErrorEvent: Boolean = false,
     ): CompletableDeferred<Any?> {
         val deferred = CompletableDeferred<Any?>()
         val id =
             send(method, params) { reqId ->
-                pendingCalls[reqId] = PendingCall(method, deferred)
+                pendingCalls[reqId] = PendingCall(method, deferred, suppressErrorEvent = suppressErrorEvent)
             }
         deferred.invokeOnCompletion { cause ->
             if (cause is CancellationException) {
@@ -1458,6 +1460,16 @@ object HermesWsClient {
                             disconnectIfIdleInBackground()
                         }
                     }
+                    if (pendingCalls[event.id]?.suppressErrorEvent == true) {
+                        // Opt-in suppression: the caller already handles the
+                        // failure through the CompletableDeferred, so the event
+                        // copy would only surface a duplicate UI banner for
+                        // optional features (e.g. "subagent.list" on gateways
+                        // without the method, issue #1089). Default request()
+                        // behavior still emits the event for shared consumers.
+                        resolvePending(event.id, null, event.error)
+                        return
+                    }
                     removeQueuedMessage(event.id)
                     resolvePending(event.id, null, event.error)
                 }

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

@@ -37,6 +37,7 @@ object SubagentRepository {
                     .request(
                         WsMethods.SUBAGENT_LIST,
                         mapOf("session_id" to sessionId),
+                        suppressErrorEvent = true,
                     ).await()
             decode<SubagentListResponse>(result)
         } catch (e: Exception) {
@@ -65,7 +66,13 @@ object SubagentRepository {
         if (sessionId.isNotBlank()) {
             params["session_id"] = sessionId
         }
-        val result = HermesWsClient.request(WsMethods.SUBAGENT_TAIL, params).await()
+        val result =
+            HermesWsClient
+                .request(
+                    WsMethods.SUBAGENT_TAIL,
+                    params,
+                    suppressErrorEvent = true,
+                ).await()
         return decode<SubagentTailResponse>(result)
     }