Find open study data for a cross-tool comparison gallery example (e.g. ReEDS vs Sienna)

Cross-tool comparison on the same system is GAT's core selling point, and the gallery has zero coverage of it — every example is single-scenario Sienna (plus the shared-API transmission example). We need openly licensed study data that can serve as a fixture for a MultiScenario / ReEDS-vs-Sienna example.

The format gap: published results on OEDI and similar open-data platforms are typically post-processed deliverables, not native solve outputs. E.g. the National Transmission Planning Study ReEDS results on OEDI are not in the standard ReEDS run-folder format that ReEDsScenario parses — so 'data exists' and 'data GAT can load' are different things today.

Paths to evaluate:

1. Survey OEDI and similar open platforms for studies published in (or convertible to) native tool formats — ideally a study with both CEM (ReEDS) and PCM (Sienna/PLEXOS-class) results for the same system.
2. Converter: a small adapter from a published-results format (e.g. the NTP Study OEDI layout) into what the ReEDS handler expects — potentially generally useful beyond the gallery, since users will hit the same gap.
3. Synthesize: a minimal ReEDS-format fixture for the same footprint as the existing Sienna RTS-GMLC fixture, so the comparison example is apples-to-apples even if stylized.

Deliverable: a gallery example demonstrating a cross-tool comparison (capacity and/or dispatch, ReEDS vs Sienna) on one system, with the fixture either downloadable or regenerable.

Constraints: data must be openly licensed and small enough for CI (or fetched on demand); any comparison example is also a natural first consumer of the units contract (#8) — cross-tool unit normalization is exactly where it earns its keep. Related: #13 (fixture horizon) if the comparison wants monthly/annual views.

Start by surveying OEDI and similar open-data platforms for openly licensed studies that can load through ReEDsScenario, checking the NTP Study layout against the expected native ReEDS run-folder format. Review the existing Sienna RTS-GMLC fixture and the related units-contract and fixture-horizon issues. Done means a downloadable or regenerable small fixture and a gallery example comparing ReEDS and Sienna capacity or dispatch on one system.