chore: remove dead system.error websocket contract (#2066)

Co-authored-by: Kandev Agent <agent@kandev.dev>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

apps/packages/types/src/backend.ts

@@ -7,7 +7,6 @@ export type BackendMessageType =
   | "agent.updated"
   | "terminal.output"
   | "diff.update"
-  | "system.error"
   | "workspace.created"
   | "workspace.updated"
   | "workspace.deleted"
@@ -75,11 +74,6 @@ export type DiffUpdatePayload = {
   }>;
 };
 
-export type SystemErrorPayload = {
-  message: string;
-  code?: string;
-};
-
 export type TaskSessionNotificationPayload = {
   task_id: string;
   session_id: string;
@@ -133,7 +127,6 @@ export type BackendMessageMap = {
   "agent.updated": BackendMessage<"agent.updated", AgentUpdatePayload>;
   "terminal.output": BackendMessage<"terminal.output", TerminalOutputPayload>;
   "diff.update": BackendMessage<"diff.update", DiffUpdatePayload>;
-  "system.error": BackendMessage<"system.error", SystemErrorPayload>;
   "workspace.created": BackendMessage<"workspace.created", WorkspacePayload>;
   "workspace.updated": BackendMessage<"workspace.updated", WorkspacePayload>;
   "workspace.deleted": BackendMessage<"workspace.deleted", WorkspacePayload>;

apps/web/lib/types/backend.ts

@@ -172,11 +172,6 @@ export type DiffUpdatePayload = {
   }>;
 };
 
-export type SystemErrorPayload = {
-  message: string;
-  code?: string;
-};
-
 export type UpdateAvailablePayload = {
   version: string;
   url?: string;
@@ -510,7 +505,6 @@ export type BackendMessageMap = OfficeBackendMessageMap &
     "terminal.output": BackendMessage<"terminal.output", TerminalOutputPayload>;
     "diff.update": BackendMessage<"diff.update", DiffUpdatePayload>;
     "session.git.event": BackendMessage<"session.git.event", GitEventPayload>;
-    "system.error": BackendMessage<"system.error", SystemErrorPayload>;
     "system.job.update": BackendMessage<"system.job.update", import("./system").SystemJob>;
     "system.metrics.updated": BackendMessage<"system.metrics.updated", SystemMetricsSnapshot>;
     "system.update_available": BackendMessage<"system.update_available", UpdateAvailablePayload>;

apps/web/lib/ws/handlers/system-events.ts

@@ -4,9 +4,6 @@ import type { WsHandlers } from "@/lib/ws/handlers/types";
 
 export function registerSystemEventsHandlers(store: StoreApi<AppState>): WsHandlers {
   return {
-    "system.error": () => {
-      // TODO: surface as toast/notification once UI is ready.
-    },
     "system.job.update": (message) => {
       // The WS payload is the full SystemJob row published by the backend
       // jobs tracker (see internal/system/jobs). Upsert by id so the