[khvn26]

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

• sdk-spec/steps.cs: one static 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
  public static async Task<IEnumerable<object>> GetEnvironmentFlags(FlagsmithClient flagsmith) =>
      AsSpecFlags(await flagsmith.GetEnvironmentFlags());

• sdk-spec/Dockerfile: builds the SDK from source and compiles the steps file with the spec's .NET harness, which supplies the project file. No .csproj lives in this repository, and nothing in sdk-spec/ is in the solution or the NuGet package.

• .github/workflows/sdk-spec.yml: calls the spec's reusable workflow with language: dotnet. It is pinned to v0.3.0. renovate.json bumps the uses: ref and spec-ref together.

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

Note: the SDK exposes every flag value as a string (IFlag.Value), so 42 becomes "42" and true becomes "true". The steps file restores numbers and booleans, which means a string value such as "42" cannot be told apart from a number.