[wangyinz]

Fixes #859.

Summary

• apply t0shift exactly once to both the requested and comparison windows
• reject reversed autopad windows and non-finite/non-positive sample intervals before allocation or mutation
• preserve one-sample equal-endpoint windows and normalize MsPASSError construction

Verification

• focused and existing window tests: 39 passed
• independent baseline check: 18 contract failures before the fix
• independent agent review: PASS, zero blockers
• Black, py_compile, and git diff --check: passed

This PR is ready for human review. It must not be merged automatically.

[codecov]

Codecov Report

❌ Patch coverage is 93.75000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 71.30%. Comparing base (431f962) to head (8845e4e).

Files with missing lines	Patch %	Lines
python/mspasspy/algorithms/window.py	93.75%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #906      +/-   ##
==========================================
+ Coverage   71.28%   71.30%   +0.01%     
==========================================
  Files         180      180              
  Lines       35475    35489      +14     
  Branches     2510     2510              
==========================================
+ Hits        25289    25304      +15     
+ Misses       9286     9285       -1     
  Partials      900      900              

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