fix(scripts): avoid overwriting git local config in e2e script

[Hweinstock]

Problem

The local e2e test script overwrites my git config, adding a testing name for user.name and user.email. This persists after running the script and causes commits to be coauthored by local e2e.

Example: 6c57e78

Solution

Remove the git config override and replace it with a warning if git is not configured. Any engineer running this would likely have git configured, but just in case we fail early.

Testing

Ran locally:

=== Assuming IAM role ===
✅ Assumed role successfully
=== Fetching API keys from Secrets Manager ===
✅ Secrets loaded (keys present: ANTHROPIC_API_KEY, CDP_API_KEY_ID, CDP_API_KEY_SECRET, CDP_WALLET_SECRET, EFS_ACCESS_POINT_ARN, FILESYSTEM_SECURITY_GROUP_ID, FILESYSTEM_SUB
NET_ID, GEMINI_API_KEY, OPENAI_API_KEY, S3_ACCESS_POINT_ARN
=== Setting AWS account env var ===
✅ AWS_ACCOUNT_ID=685197708687  AWS_REGION=us-east-1
=== Verifying git is configured (required for agentcore create) ===
git configured as: Hweinstock <hkobew@amazon.com>
=== Installing dependencies ===

[agentcore-devx-automation]

Claude Security Review: no high-confidence findings. (run)

[github-actions]

Package Tarball

aws-agentcore-0.19.0.tgz

How to install

gh release download pr-1501-tarball --repo aws/agentcore-cli --pattern "*.tgz" --dir /tmp/pr-tarball
npm install -g /tmp/pr-tarball/aws-agentcore-0.19.0.tgz

[agentcore-cli-automation]

Clean, focused fix. The script-only change correctly stops mutating the developer's global git config and fails early with a clear error message if git isn't configured. Verified the || true fallback handles the unset-config case correctly under set -euo pipefail. Using --global as the scope is appropriate since agentcore create operates outside this repo's local config. No tests or telemetry needed for a dev-only script change.