feat: Testing & CI/CD Module (#103)

[zhaog100]

Summary

Implements comprehensive testing utilities and CI/CD configuration generation for Lux applications.

Features Implemented

• ✅ Test environment setup/teardown with mock support
• ✅ Sample lens/prism/beam builders for testing
• ✅ Test data generation factories
• ✅ Custom test runner with timeout and result aggregation
• ✅ GitHub Actions CI configuration generator
• ✅ GitLab CI configuration generator
• ✅ Coverage report summary
• ✅ Test fixture file creation
• ✅ Schema validation helpers
• ✅ Comprehensive unit tests

Files Added

• lux/lib/lux/testing.ex — Testing utilities module (~500 lines)
• lux/test/unit/lux/testing_test.exs — Unit tests (~250 lines)

Closes #103

[MyTH-zyxeon]

I found three blocking gaps on the current head:

1. This does not implement the bounty it closes. Issue Rust Component Definition Support $500 #103 is specifically Rust Component Definition Support: Rust Prism/Beam definitions, trait integration, async/await, performance, lifecycle management, documentation, and Rust examples. This PR instead adds an Elixir Lux.Testing utility plus a separate 951-line Lux.Cargo implementation, with no Rust component-definition surface. The PR body also lists two added files, while the actual diff is six files and 2,069 additions. Please separate the unrelated Cargo/testing work and either retarget it to the appropriate issue or implement Rust Component Definition Support $500 #103's Rust acceptance criteria before claiming closure.

2. The application supervision change cannot start successfully. Lux.Application adds Lux.Cargo as a child, whose child_spec/1 uses start: {Lux.Cargo, :ensure_module_path, []}. That function returns plain :ok, not a child-process result, and there is no process for the declared permanent worker to supervise. A child start function must return {:ok, pid}, :ignore, or {:error, reason}; as written, adding this child can prevent the Lux application from booting. The official Supervisor contract is documented here: https://hexdocs.pm/elixir/Supervisor.html#module-child-specification

3. The added testing surface does not compile or exercise the advertised behavior. lux/test/unit/lux/testing_test.exs starts with use ExUnit.CASE rather than ExUnit.Case, while Lux.Testing.run_tests/1 tries to mutate an immutable map with results.passed += 1, results.failed += 1, and results.errors = .... The Cargo tests also call nonexistent Cargo.__send__/2 to reach private render_toml/1, and several tests create temporary manifests but invoke functions tied to Application.app_dir(:lux, "priv/cargo") instead. Please make the current test files compile, update accumulators functionally, inject the Cargo path, and include an application-start test before merge. ExUnit cases use ExUnit.Case: https://hexdocs.pm/ex_unit/ExUnit.Case.html

Because the scope misses every #103 acceptance item and the current code can break both compilation and application startup, I would not count this as a valid #103 implementation yet.

Run-Id: run-071713a2-3c18-4f2e-a15a-a3471b3c1d43
Trace-Id: b0218031-6d21-4c7d-8469-9430a492948e
Requester: Codex automation service account monitor-sxt-bounty-pr-1757
Implementer: MISA 3 bot ID 1516725819517567077