[FIX] Notebook AWS_REGION in .env and NextGen OpenSearch VPC endpoint

[oussamahansal]

Description

Two fixes for the lexical-graph CloudFormation templates

Changes

• Write AWS_REGION into the notebook .env
• Use a standard EC2 interface VPC endpoint for the NextGen collection

Problem

Related issue (if any): #

Testing

• Unit tests added/updated
• Integration tests added (as appropriate)
• Existing tests pass (pytest)
• Tested manually (describe below)

Checklist

• Code follows existing style and conventions
• License headers present on new files
• Documentation updated (if applicable)
• No breaking changes (or clearly documented)

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[mykola-pereyma]

On the AWS_REGION change: every template already exports AWS_REGION into the notebook .env on main, so these additions are duplicates (one per template; existing-vpc ends up with three). Details inline. Harmless at runtime but redundant — suggest dropping the AWS_REGION additions unless there's a path where it's actually missing.

(Separately, the NextGen VPC-endpoint type swap is the substantive change and would benefit from confirmation it was deployed end-to-end — the AOSS network policy still references this endpoint in SourceVPCEs, and swapping the AOSS-managed endpoint for a generic EC2 interface endpoint needs to be verified against a live collection.)

[mykola-pereyma]

For the NextGen VPC-endpoint change (Change 2): it's a structurally sound CloudFormation swap, but its actual functioning depends on two AOSS control-plane behaviors that aren't verifiable from the template. Could you provide deploy confirmation? Specifics inline on the endpoint's ServiceName.

[noel-improv]

The change looks good, just one blocking item and suggestions referenced below

[github-actions]

Lexical Graph Coverage Report: The coverage is at 65.82% (target: 80%). Download the HTML report here.

[mykola-pereyma]

LGTM

[noel-improv]

lgtm, thanks for addressing the raised items