Implement reversible PII de-identification round trip (T1–T7)

Build the AWS side of the HNCB demo end to end (region ap-southeast-1):

- T1 /tokenize + T2 /restore: Lambdas behind a public API Gateway (shared-secret
  auth), Presidio detection, random per-request tokens, DynamoDB vault; overlap
  resolution so a ROC ID stays TW_ROC_ID.
- T3: Presidio made private (SG-locked to the tokenize Lambda in-VPC; DynamoDB
  gateway endpoint); only /tokenize + /restore are public.
- T4: RAG Lambda registered as an MCP tool on an AgentCore Gateway (AWS_IAM/SigV4);
  agentcore_setup.sh + a SigV4 MCP invoke test.
- T5: Strands agent deployed to AgentCore Runtime; SigV4 gateway auth, apac
  inference profile, pinned deps.
- T6: advisor UI on S3+CloudFront with a Fusion-less demo orchestrator (/demo)
  chaining tokenize -> runtime -> restore.
- T7: README runbook + trace check; teardown deletes gateway/runtime/memory/ECR.

Verified live: the cloud AgentCore/Bedrock trace shows only tokens, never the
real name. Secrets stay in gitignored local.auto.tfvars.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

agent/requirements.txt

@@ -1,4 +1,6 @@
-bedrock-agentcore
-strands-agents
-mcp
-boto3
+# Pinned before `agentcore launch` (versions resolved 2026-07-01). These SDKs move
+# fast; re-resolve and re-pin if you rebuild.
+bedrock-agentcore==1.16.0
+strands-agents==1.45.0
+mcp==1.28.1
+boto3==1.43.38