Fix vectorized boolean signature

[EltonChang1]

Relevant Issue(s)/PR(s)

Fixes #979.

Provide an overview of the implemented solution or the fix and elaborate on the modifications.

Newer Numba versions evaluate signature strings against numba.types, where bool(...) resolves to Python's built-in bool and raises TypeError: bool expected at most 1 argument, got 6 during Stingray import.

This changes the check_powers_for_intrinsic_coherence vectorized signatures to use Numba type objects with an explicit boolean return type instead of parsing bool(...) strings. It also exposes boolean through Stingray's Numba compatibility wrapper, adds scalar regression coverage for the affected function, and includes a bugfix changelog fragment.

Is there a new dependency introduced by your contribution? If so, please specify.

No new dependencies.

Any other comments?

Validation performed:

• .venv/bin/python -m pytest stingray/tests/test_fourier.py -q with NumPy 2.4.6, Astropy 8.0.0, Numba 0.65.1: 199 passed.
• .venv/bin/python -m pytest stingray/tests/test_fourier.py -k check_powers_for_intrinsic_coherence -q with NumPy 1.24.4, Astropy 6.1.3, Matplotlib 3.10.9, Numba 0.65.1: 1 passed, 198 deselected.
• Manual import check with NumPy 1.24.4, Astropy 6.1.3, Matplotlib 3.10.9, Numba 0.65.1: import stingray succeeds and check_powers_for_intrinsic_coherence(...) returns normally.
• git diff --check.

Limitations: I did not run the full repository test suite.

AI disclosure: OpenAI Codex/ChatGPT was used to inspect the issue, identify the affected signature, make the code/test/changelog edits, and draft this PR description. The final patch was validated locally with the checks listed above.

[matteobachetti]

@EltonChang1 thanks for your PR! Please fix the name of the change log ;)

[EltonChang1]

Fixed in 74b8ee5: the Towncrier fragment is now docs/changes/980.bugfix.rst, matching this PR number. The focused coherence-power regression still passes (1 passed, 198 deselected), and git diff --check passes.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 80.39%. Comparing base (840569c) to head (74b8ee5).

Files with missing lines	Patch %	Lines
stingray/utils.py	50.00%	1 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (840569c) and HEAD (74b8ee5). Click for more details.

HEAD has 99 uploads less than BASE

Flag	BASE (840569c)	HEAD (74b8ee5)
	103	4

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #980       +/-   ##
===========================================
- Coverage   96.23%   80.39%   -15.85%     
===========================================
  Files          48       48               
  Lines       10099    10099               
===========================================
- Hits         9719     8119     -1600     
- Misses        380     1980     +1600     

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[EltonChang1]

Addressed the patch-coverage failure in 4f0a672 by separating the no-Numba boolean fallback alias and marking that import-fallback-only line with the project’s existing coverage pragma. Focused validation passes: the coherence-power regression (1 passed, 198 deselected), the full Fourier test module (199 passed), and git diff --check. The link-check failure is unrelated to this change; it reports pre-existing external URLs in docs/history.rst, docs/contributing.rst, and the modeling notebook.