degeneracystructure strides sectorstructure's flat tree list assuming: (1) contiguous grouping by coupled sector, (2) f₂-major/f₁-minor ordering, (3) every f₂ for a given c has the same number n₁ of f₁ partners. Only documented as "canonical order"; only checked post-hoc via a length assertion. Also relies on _blocksectors guaranteeing n₁ ≥ 1 (a fact that lives in a different file: homspace.jl). Document these invariants explicitly (docstring + a cheap debug assertion) since they're load-bearing for tensor data layout.
src/spaces/structure.jl:41-72 (producer), :131-184 (consumer).
degeneracystructurestridessectorstructure's flat tree list assuming: (1) contiguous grouping by coupled sector, (2) f₂-major/f₁-minor ordering, (3) every f₂ for a givenchas the same numbern₁of f₁ partners. Only documented as "canonical order"; only checked post-hoc via a length assertion. Also relies on_blocksectorsguaranteeingn₁ ≥ 1(a fact that lives in a different file:homspace.jl). Document these invariants explicitly (docstring + a cheap debug assertion) since they're load-bearing for tensor data layout.src/spaces/structure.jl:41-72(producer),:131-184(consumer).