test(CLI): add test harness

[jablan]

Adds a simple ruby/rspec/rack based test harness for CLI integration tests.

So far, contains only a basic test, but provides a way to mock API responses and assert requests performed by the CLI app.

[Copilot]

Pull request overview

This PR introduces a Ruby/RSpec-based integration test harness for the CLI, enabling mocked HTTP responses and request assertions. The implementation uses a Rack-based mock server that runs alongside the CLI binary during test execution.

Changes:

• Added a Rack-based mock server with control endpoints for setting responses and inspecting captured requests
• Created helper modules and RSpec configuration for managing the mock server lifecycle
• Implemented a basic integration test demonstrating authenticated API requests
• Updated CI workflow to run integration tests alongside existing unit tests

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
clients/cli/spec/support/mock_server.ru	Rack application providing mock HTTP server with control API for test setup and request recording
clients/cli/spec/support/mock_control.rb	Ruby module providing helper methods to interact with mock server control endpoints
clients/cli/spec/spec_helper.rb	RSpec configuration managing mock server lifecycle and CLI execution helpers
clients/cli/spec/cli_spec.rb	Integration test verifying CLI can authenticate and make API requests
clients/cli/Gemfile	Dependencies for the test harness (rspec, rack, rackup, webrick)
.github/workflows/test-cli.yml	CI workflow updates to run integration tests with Ruby setup

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