Common interface implemented by every GGUF-quantized zero-shot time-series
forecaster in the workspace (Toto, Chronos, TimesFM, …). Lets the CLI and
Python bindings dispatch across models without per-model glue code.
Turn one forecast’s QuantileMatrix into a ForecastOutput, choosing the
univariate (flat point/quantiles) or multivariate (variates: [...])
shape based on how many variates the matrix actually has.