add percentiles for each serie

[jobo322]

it would be used to select the min level of contour plot.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.36%. Comparing base (9ae3772) to head (edd8ea0).
⚠️ Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #397      +/-   ##
==========================================
+ Coverage   97.13%   97.36%   +0.23%     
==========================================
  Files         209      213       +4     
  Lines        4159     4258      +99     
  Branches     1037     1063      +26     
==========================================
+ Hits         4040     4146     +106     
+ Misses        115      109       -6     
+ Partials        4        3       -1     

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[Copilot]

Pull request overview

This PR extends the xNoiseSanPlot output to include computed intensity percentiles (intended to help choose contour plot minimum levels), and updates the implementation/tests accordingly.

Changes:

• Add percentiles (positive/negative) to XNoiseSanPlotResult and compute them in xNoiseSanPlot.
• Introduce getPercentiles() to compute 50th–99.5th percentiles (0.5 step) from the pre-sorted sign arrays.
• Adjust determineCutOff()’s sigma-estimation scan to use the considerList range, and update tests to assert the new percentiles output.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/x/xNoiseSanPlot.ts	Adds percentile output + helper; modifies cut-off estimation loop and minor refactors/cleanup.
src/x/tests/xNoiseSanPlot.test.ts	Adds assertions for the new percentiles fields on the result.

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