Derive named auxiliary legs in project

[mtfishman]

Summary

The named project, tryproject, and unchecked_project methods (the ones taking NamedUnitRange indices) now derive a named auxiliary leg for each surplus axis of the input array. When the array carries more axes than the codomain and domain indices account for, each extra trailing axis is an auxiliary leg the backend added to keep the result symmetry-allowed, for example a flux-canceling charge leg for a charge-shifting operator like Cdag. Those axes now come back as named dimensions with freshly minted names, so a caller can read them off the result.

An operator that shifts charge can then be built directly through project by reshaping its dense matrix to a trailing length-1 axis: project(reshape(m, (size(m)..., 1)), (i', ), (i,)) returns the operator with its flux carried on a named aux index. The bare graded-space form already derived this axis, but the named wrappers passed it through unnamed.

Also qualifies space, dim, dual, and scalar as TK.* in the TensorKit-extension tests. ITensorBase marks space public, so an unqualified using TensorKit: space clashes with it when the tests run in a session that already has ITensorBase's space in scope.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.06%. Comparing base (d963009) to head (aee7097).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #231      +/-   ##
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+ Coverage   78.02%   78.06%   +0.03%     
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  Files          30       30              
  Lines        1734     1737       +3     
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+ Hits         1353     1356       +3     
  Misses        381      381              

Flag	Coverage Δ
docs	26.95% <71.42%> (+0.10%)	⬆️

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