Guard β=0 in 0-dim bipermutedimsopadd! and drop empty-array workaround

[mtfishman]

Summary

• The 0-dim branch of bipermutedimsopadd! read dest[] unconditionally (β * dest[] + α * op(src[])), even when β = 0. By BLAS convention, β = 0 means dest is treated as write-only — its contents need not be defined. With element types whose undef storage is unreadable, the unguarded read crashed: bipermutedimsopadd!(Array{BigFloat, 0}(undef), identity, src, (), (), true, false) threw UndefRefError, since the unassigned slot of a 0-dim array of mutable BigFloat cannot be read. This surfaced via callers that allocate a 0-dim destination via similar and call into bipermutedimsopadd! with β = 0 (e.g. scalar contractions producing a 0-dim result).
• Adds an iszero(β) guard to the 0-dim branch to skip reading dest in the write-only case. The 0-dim short-circuit itself is kept: it lets downstream array types (e.g. BlockSparseArray{T, 0}) use direct dest[]/src[] accesses instead of having to support getindex on a 0-dim PermutedDimsArray wrapper around their type.
• The companion isempty(dest) && return dest early return worked around a Strided.jl broadcasting bug fixed by QuantumKitHub/Strided.jl#50, released in Strided 2.3.5. Adds Strided to [deps] (with using Strided: Strided so it isn't reported as stale) and a Strided = "2.3.5" compat floor, then drops the workaround.
• Adds a regression test covering Array{T, 0} for T ∈ {Float64, BigFloat} with both β = 0 (write-only) and β ≠ 0 (accumulating) cases.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.39%. Comparing base (b4f43b6) to head (6b18f18).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #173      +/-   ##
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+ Coverage   80.37%   80.39%   +0.02%     
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  Files          24       24              
  Lines         963      964       +1     
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+ Hits          774      775       +1     
  Misses        189      189              

Flag	Coverage Δ
docs	0.00% <0.00%> (ø)

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