feat: expose stop_reason on SDKResultMessage (#30)

src/session.ts

@@ -408,12 +408,14 @@ export class Session implements AsyncDisposable {
         duration_ms: number;
         total_cost_usd?: number;
         conversation_id: string;
+        stop_reason?: string;
       };
       return {
         type: "result",
         success: msg.subtype === "success",
         result: msg.result,
         error: msg.subtype !== "success" ? msg.subtype : undefined,
+        stopReason: msg.stop_reason,
         durationMs: msg.duration_ms,
         totalCostUsd: msg.total_cost_usd,
         conversationId: msg.conversation_id,

src/types.ts

@@ -279,6 +279,7 @@ export interface SDKResultMessage {
   success: boolean;
   result?: string;
   error?: string;
+  stopReason?: string;
   durationMs: number;
   totalCostUsd?: number;
   conversationId: string | null;