Forward live usage stream events

The wire schema already allowed completed-turn usage, but rejected active usage updates before clients could see them. Accept usage_updated payloads and preserve turn ids on streamed turn events.

packages/protocol/src/messages.ts

@@ -594,11 +594,19 @@ export const AgentStreamEventPayloadSchema = z.discriminatedUnion("type", [
   z.object({
     type: z.literal("turn_started"),
     provider: AgentProviderSchema,
+    turnId: z.string().optional(),
   }),
   z.object({
     type: z.literal("turn_completed"),
     provider: AgentProviderSchema,
     usage: AgentUsageSchema.optional(),
+    turnId: z.string().optional(),
+  }),
+  z.object({
+    type: z.literal("usage_updated"),
+    provider: AgentProviderSchema,
+    usage: AgentUsageSchema,
+    turnId: z.string().optional(),
   }),
   z.object({
     type: z.literal("turn_failed"),
@@ -606,27 +614,32 @@ export const AgentStreamEventPayloadSchema = z.discriminatedUnion("type", [
     error: z.string(),
     code: z.string().optional(),
     diagnostic: z.string().optional(),
+    turnId: z.string().optional(),
   }),
   z.object({
     type: z.literal("turn_canceled"),
     provider: AgentProviderSchema,
     reason: z.string(),
+    turnId: z.string().optional(),
   }),
   z.object({
     type: z.literal("timeline"),
     provider: AgentProviderSchema,
     item: AgentTimelineItemPayloadSchema,
+    turnId: z.string().optional(),
   }),
   z.object({
     type: z.literal("permission_requested"),
     provider: AgentProviderSchema,
     request: AgentPermissionRequestPayloadSchema,
+    turnId: z.string().optional(),
   }),
   z.object({
     type: z.literal("permission_resolved"),
     provider: AgentProviderSchema,
     requestId: z.string(),
     resolution: AgentPermissionResponseSchema,
+    turnId: z.string().optional(),
   }),
   z.object({
     type: z.literal("attention_required"),