* ci(review): Add Muse Spark 1.3 contributor as AI reviewer Run a third PR review job via the OpenCode Go contributor route (opencode-go/muse-spark-1.3-contributor), alongside the existing OpenCode and Claude reviews. Authenticates with OPENCODE_API_KEY. Note: the contributor route is discounted in exchange for Meta/OpenCode being allowed to use prompts and completions for training/feedback. * ci(review): Use Zen contributor-free route for Muse Spark reviewer Swap opencode-go/muse-spark-1.3-contributor for opencode/muse-spark-1.3-contributor-free: the account uses OpenCode Zen credits, not a Go subscription. The Zen route is free (limited-time feedback route) and still requires the workspace opt-in for models that train on request data.