Honor the exact light-time convergence tolerance

[sylvesterkaczmarek]

Apply the existing 1 ps tolerance to each light-time update before reducing the convergence condition. The previous np.any(abs(delta)) > 1e-12 compared a Boolean with the tolerance, effectively requiring bitwise-stable delays.

This can reject already-converged observations when floating-point epoch rounding produces a sub-picosecond cycle. Two real Keplerian examples reproduce the failure in radec(..., obsAngleCorrection="exact"). The numerical tolerance and iteration limit are unchanged; nonconvergent and NaN updates still raise.

Validation

Python 3.12, NumPy 2.5.3, SciPy 1.18.1 on macOS arm64:

• New regressions on unchanged main (8bb784c): 4 failed, 2 passed. With the fix: all 6 passed.
• Coverage includes multi-orbit convergence, nonconvergence/NaN controls, and public RA/Dec and direction-cosine results checked against an independently bracketed light-time root.
• Focused compute tests: 23 passed.
• Full suite: 334 passed, 2 skipped, 35 subtests passed.
• New tests pass Flake8; no additional Flake8 findings in compute.py. Syntax checks and git diff --check pass.

No native code or public API changes. Other operating systems were not tested locally.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.39%. Comparing base (8bb784c) to head (0f9a368).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #146   +/-   ##
=======================================
  Coverage   97.39%   97.39%           
=======================================
  Files          17       17           
  Lines        5897     5897           
=======================================
  Hits         5743     5743           
  Misses        154      154           

Flag	Coverage Δ
unittests	97.39% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
ssapy/compute.py	94.93% <100.00%> (ø)

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[sylvesterkaczmarek]

Thank you for merging this. Much appreciated, and I’m glad to keep contributing to SSAPy.