maths/radix2_fft.py: Fix calculation for Python 3.14 (#12772)

* maths/radix2_fft.py: Fix calculation for Python 3.14

As suggested at:
* #12729 (comment)
* #12710 (comment)

@MaximSmolskiy @KirilBangachev @skirpichev Careful review, please.  I am just implementing the suggestion, but I do not have any expertise in this area.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Change test results

* GitHub Actions: Rename job from build to directory_writer

It is confusing to have two jobs named `build`.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: cclauss

.github/workflows/directory_writer.yml

@@ -3,7 +3,7 @@
 name: directory_writer
 on: [push]
 jobs:
-  build:
+  directory_writer:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4

maths/radix2_fft.py

@@ -40,13 +40,13 @@ class FFT:
 
     Print product
     >>> x.product  # 2x + 3x^2 + 8x^3 + 4x^4 + 6x^5
-    [(-0+0j), (2+0j), (3+0j), (8+0j), (6+0j), (8+0j)]
+    [(-0-0j), (2+0j), (3-0j), (8-0j), (6+0j), (8+0j)]
 
     __str__ test
     >>> print(x)
     A = 0*x^0 + 1*x^1 + 2*x^0 + 3*x^2
     B = 0*x^2 + 1*x^3 + 2*x^4
-    A*B = 0*x^(-0+0j) + 1*x^(2+0j) + 2*x^(3+0j) + 3*x^(8+0j) + 4*x^(6+0j) + 5*x^(8+0j)
+    A*B = 0*x^(-0-0j) + 1*x^(2+0j) + 2*x^(3-0j) + 3*x^(8-0j) + 4*x^(6+0j) + 5*x^(8+0j)
     """
 
     def __init__(self, poly_a=None, poly_b=None):
@@ -147,7 +147,9 @@ def __multiply(self):
             inverce_c = new_inverse_c
             next_ncol *= 2
         # Unpack
-        inverce_c = [round(x[0].real, 8) + round(x[0].imag, 8) * 1j for x in inverce_c]
+        inverce_c = [
+            complex(round(x[0].real, 8), round(x[0].imag, 8)) for x in inverce_c
+        ]
 
         # Remove leading 0's
         while inverce_c[-1] == 0: