fix(payments): self-heal empty aws-targets.json before T02 deploy

01-features/08-agents-that-transact/00-getting-started/02-deploy-to-agentcore-runtime/README.md

@@ -138,6 +138,13 @@ npm install -g @aws/agentcore
 agentcore --version
 ```
 
+### agentcore deploy fails with `Target "default" not found in aws-targets.json`
+
+Some agentcore CLI versions scaffold `<project>/agentcore/aws-targets.json` as an empty list, which makes `agentcore deploy` exit before the CDK synth. The `deploy_payment_agent.py` script appends a `default` entry automatically when it sees this. If you ran `agentcore deploy` directly, write the file by hand and re-run:
+```bash
+echo '[{"name":"default","account":"<account-id>","region":"<region>"}]' > PaymentAgent/agentcore/aws-targets.json
+```
+
 ### Deploy fails with CDK bootstrap error
 
 Bootstrap CDK in your account/region first:

01-features/08-agents-that-transact/00-getting-started/02-deploy-to-agentcore-runtime/deploy_payment_agent.py

@@ -146,6 +146,27 @@
 
 print("pyproject.toml updated")
 
+# Some agentcore CLI versions scaffold aws-targets.json as an empty list,
+# which causes `agentcore deploy` to exit with `Target "default" not found
+# in aws-targets.json`. Append a default target if one is missing, and leave
+# any other entries alone.
+targets_file = os.path.join(project_dir, "agentcore", "aws-targets.json")
+if os.path.exists(targets_file):
+    try:
+        with open(targets_file) as f:
+            targets = json.loads(f.read() or "[]")
+    except json.JSONDecodeError:
+        targets = None
+    if (
+        isinstance(targets, list)
+        and all(isinstance(t, dict) and "name" in t for t in targets)
+        and not any(t["name"] == "default" for t in targets)
+    ):
+        targets.append({"name": "default", "account": account_id, "region": REGION})
+        with open(targets_file, "w") as f:
+            f.write(json.dumps(targets, indent=2))
+        print(f"Added default target to aws-targets.json (account={account_id}, region={REGION})")
+
 # ── Step 7: Deploy to AgentCore Runtime ───────────────────────────────────────
 print("\n── Step 7: Deploy to AgentCore Runtime ──")
 print("This creates billable AWS resources (Lambda, CloudWatch, API Gateway).")