[mtfishman]

Summary

Sector(U1(0), fSU2(0)) built a product holding another product as a factor, rather than the flat U1(0) × fSU2(0) that was almost always meant, and TensorKitSectors cannot infer the fusion and braiding styles of the nested product. Sector now throws for a positional product factor and points to sectorproduct (or ×), which splices it in.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.79%. Comparing base (a906086) to head (7f3c2b3).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #290      +/-   ##
==========================================
+ Coverage   85.78%   85.79%   +0.01%     
==========================================
  Files          40       40              
  Lines        2842     2845       +3     
==========================================
+ Hits         2438     2441       +3     
  Misses        404      404              

Flag	Coverage Δ
docs	16.87% <100.00%> (+0.06%)	⬆️

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