Compare with the fill value by identity in the non-zero-preserving map and broadcast kernels

[ViralBShah]

map and broadcast! of a function that is not zero at zero compare each result with the fill value f(0) using !=. That throws when the comparison is missing, and it leaves the fill value in place of a result that equals it but has another type.

Before

julia> A = sparse([1.0 0; 0 2.0]);

julia> map(x -> x == 0 ? 1.0 : missing, A)
ERROR: TypeError: non-boolean (Missing) used in boolean context

julia> typeof.(map(x -> x == 0 ? 1 : 1.0, A))
2×2 Matrix{DataType}:
 Int64  Int64
 Int64  Int64

After

julia> map(x -> x == 0 ? 1.0 : missing, A)
2×2 SparseMatrixCSC{Union{Missing, Float64}, Int64} with 4 stored entries:
  missing  1.0
 1.0        missing

julia> typeof.(map(x -> x == 0 ? 1 : 1.0, A))   # as for Array(A)
2×2 Matrix{DataType}:
 Float64  Int64
 Int64    Float64

The _map_notzeropres! and _broadcast_notzeropres! kernels (one, two and N arguments) fill the destination with f(0) and then skip the store of a result that equals it. They now skip only a result that is identical to it (!==/===), which is always a Bool and is the only case in which the store is redundant.

Time at 10^6 stored entries (4000×4000, x -> x + 1.0 and (x, y) -> x + y + 1.0, Float64, minimum of 15 runs): the one-argument kernel is unchanged (map! 13.0 ms on both), the two-argument kernel goes from 18.6 ms to 21.1 ms in map! and from 36–39 ms to 38–40 ms in map. Allocations are unchanged.

Split from #1022.

Backport candidate: a bug fix, with no new method and no change of a result type that was computed correctly before.

Written by Claude Code.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.76%. Comparing base (ead43a0) to head (590b19e).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1087   +/-   ##
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  Coverage   94.76%   94.76%           
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  Files          16       16           
  Lines        9983     9983           
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  Hits         9460     9460           
  Misses        523      523           

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[ViralBShah]

Reviewed by Codex at e4b76b0.

No actionable findings. Identity is the appropriate criterion for skipping these stores: it preserves distinct equal-valued results and avoids a non-Boolean comparison for missing. The change covers all arities and both broadcast expansion directions.