[khvn26]

Runs the Flagsmith SDK behavioural spec against this SDK on every pull request and push to main.

• sdk-spec/steps.rb: one method per SDK step, marked with the Gherkin step text as a comment. It contains only SDK calls and the mapping to the spec's flag shape, so it doubles as a CI-checked usage example:

  # When the application gets the environment flags
  def get_environment_flags(flagsmith)
    as_spec_flags(flagsmith.get_environment_flags)
  end

• sdk-spec/Dockerfile: builds and installs the gem from source, and runs the steps file under the spec's Ruby harness, taken from the harness build context. The harness speaks JSON lines over stdio, so there is no HTTP server in this repo.

• .github/workflows/sdk-spec.yml: calls the spec's reusable workflow with language: ruby. It is pinned to v0.3.0.

• renovate.json: bumps the uses: ref and spec-ref together.

• flagsmith.gemspec: excludes sdk-spec/ from the published gem.

The spec currently covers getting environment flags and getting identity flags with traits.