madness::conj(x) for double x truncated to float

[evaleev]

this seemingly is not used everywhere where "conj" is performed (there are other "instances" of conj) but most notably matrix_inner uses it ... perhaps used elsewhere also?

[Copilot]

Pull request overview

This pull request fixes a precision bug where conj(x) for double values was being truncated to float, causing loss of precision. The bug was caused by the original implementation having static double conj(float x), which forced implicit narrowing conversion when called with double arguments.

Changes:

• Converted the conj functions to templates that work with any floating-point type
• Added proper type constraints using std::enable_if_t and std::is_floating_point_v
• Changed complex conjugate function to use pass-by-reference for better performance

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[evaleev]

for the record: issue introduced in e9dae0a, code before should have been fine.