test: scaffold pinned AWS client compatibility contracts

[skyoo2003]

Summary

Adds the initial, pinned client-contract test foundation for boto3, AWS CLI, and Terraform. This is a draft: AWS CLI CRUD scenarios, Terraform modules/lifecycle coverage, CI integration, and full-suite validation remain.

Related Issue

Fixes #

Changes

• Pin boto3, AWS CLI, Terraform, and the AWS Provider contract versions.
• Add signed project-local installer scaffolding and pinned-binary validation.
• Add shared AWS CLI/Terraform pytest fixtures and initial Terraform provider configuration.

Test Plan

• pytest test/compatibility/test_client_tools.py test/compatibility/test_terraform.py::test_terraform_configuration_pins_aws_provider -v
• Pre-commit format and lint hooks

Checklist

• Self-reviewed the code
• Added/updated tests
• Lint/format passes (pre-commit hooks)
• Updated documentation (follow-up work)
• Changie changelog fragment — N/A (draft test scaffolding)