Compare two bands at the same cell. Scalar pair → metric=delta, value=b-a. Vector pair (equal dim) → metric=cosine + per-dim delta. Returns a signed receipt naming both source fact CIDs.
When to use: Call when the user wants cross-source consistency at one place ('does Cop-DEM agree with GMRT here?'), cross-vintage drift ('how did the embedding change between 2017 and 2024 at this cell?'), or any band-vs-band comparison within a single cell. `cell` + `a` + `b` are required. `tslot_a`/`tslot_b` are OPTIONAL: omit them to let the responder auto-pick each band's latest attested tslot — required for medium/fast-tempo bands (NDVI 30-day, MODIS 8-day, weather, CAMS) where there is no fact at tslot=0. The response carries `tslot_resolution` (echoes what was chosen and why) and `bands_with_no_history` (lists any band the cell has no attested fact for).
Connector