mix aurora.snippets (Aurora UI v0.1.1)

Keeps example code shown in the docs synchronized with real, compiled, testable source so a stale snippet fails CI instead of misleading a reader.

Snippets live in docs/snippets/*.exs. Each file is a self-contained, compilable Elixir module using Aurora UI components. The docs and the component lab render these same modules, so what a reader copies is what CI compiled.

mix aurora.snippets           # compile every snippet, fail on error
mix aurora.snippets --check   # same, used in CI (alias `mix check`)

A missing docs/snippets directory is not an error before any snippet exists; the task reports "no snippets" and succeeds so the build bootstraps cleanly.