Add full suite of live integration tests for CLI validation

[tinkermonkey]

Overview

Add a comprehensive suite of live integration tests that validate the code-wrapper CLI is functional end-to-end. Tests should exercise real invocations against a live environment rather than mocked dependencies.

Goals

• Validate all CLI entry points execute without error
• Confirm correct output format and exit codes for success and failure cases
• Cover core wrapping behaviors (input passthrough, output capture, error propagation)
• Ensure the test suite can run in CI and locally

Acceptance Criteria

• Integration test runner configured (pytest or equivalent)
• Tests invoke the CLI binary directly, not internal Python modules
• At least one test per CLI command/subcommand
• Tests pass against a clean environment with no pre-existing state
• CI workflow updated to run integration tests on PR and main push
• README updated with instructions for running integration tests locally

[tinkermonkey]

📋 Requirements analysis moved to Discussion #3

This issue will be updated with final requirements when ready for implementation.

Link: #3

[tinkermonkey]

✅ Feature Complete

All sub-issues have been completed and changes have been committed.

Pull Request: #11

The PR is now ready for review and can be merged when approved.