feat: add support for T0 (theforecastingcompany/t0-alpha)

[GeoffNN]

Summary

Adds T0, The Forecasting Company's open-weights time series foundation model, as a new foundation forecaster. T0 (t0-alpha, ~102M params, Apache-2.0) is a decoder-style patch transformer producing probabilistic multi-horizon quantile forecasts — currently #1 on the fev-bench leaderboard (skill score 42.2) and CRPS 0.4941 on GIFT-Eval.

(Disclosure: I work at The Forecasting Company.)

Changes

• timecopilot/models/foundation/t0.py — T0 forecaster wrapping the tfc-t0 package, following the existing foundation-model pattern (_get_model context manager, TimeSeriesDataset batching, QuantileConverter for levels/quantiles). The model predicts 5 quantile knots and interpolates arbitrary requested levels in a single forward pass; the median is the point forecast. Ragged batches are left-padded with NaN, which T0 treats as missing.
• pyproject.toml — tfc-t0>=0.1.2 for Python 3.11–3.13 (the package's supported range), mirroring the TiRex/uni2ts marker pattern.
• tests/models/conftest.py — T0(context_length=256, batch_size=2) added to the model matrix under a version guard, plus a test_t0_import_fails guard test mirroring TiRex/Sundial.
• Docs: API reference entry + Model Hub listing.

Status

Note

Draft until tfc-t0 0.1.2 lands on PyPI (in flight): it's a metadata-only release relaxing the einops/jaxtyping floors so tfc-t0 coexists with timecopilot-uni2ts (einops==0.7.*, jaxtyping<0.3). Once published I'll regenerate uv.lock and mark this ready. With those floors, uv lock resolves cleanly (verified locally).

Validation

Run locally on macOS / Python 3.12 (with the 0.1.2 floors):

• forecast with defaults, quantiles=[0.1, 0.5, 0.9], and level=[80] on multi-series daily data: correct columns, finite values, monotone quantiles, median == point forecast.
• cross_validation(df, h=6): correct shape and columns.
• uv run pytest tests/models/test_models.py::test_t0_import_fails (skips on 3.11–3.13, asserts ImportError outside).
• ruff check + ruff format --check pass on the new/changed files.

🤖 Generated with Claude Code

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