docs: add adjustment family doctest examples

[EKtheSage]

Summary: Add Sphinx doctest examples for correlation, BERQ/Sherman, bootstrap, parallelogram, trend, constant development, and Munich adjustment docs. Split from the larger #792 work and intentionally excludes .github/workflows/sync-main-to-docs.yml. Refs #704

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Note

Low Risk
Low risk: changes are limited to docstring updates (Sphinx doctest examples and minor wording/formatting tweaks) with no intended runtime behavior changes.

Overview
Adds Sphinx doctest-ready Examples blocks to several public APIs (BerquistSherman, BootstrapODPSample, ParallelogramOLF, Trend, DevelopmentCorrelation/ValuationCorrelation, DevelopmentConstant, MunichAdjustment) to demonstrate parameter effects with reproducible outputs.

Also makes small docstring cleanups (parameter wording/formatting and a minor whitespace fix) to improve generated documentation consistency.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.23%. Comparing base (72b270c) to head (1b4b2fd).

Additional details and impacted files

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##             main     #800   +/-   ##
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  Coverage   86.23%   86.23%           
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  Files          86       86           
  Lines        4947     4947           
  Branches      643      643           
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  Hits         4266     4266           
  Misses        484      484           
  Partials      197      197           

Flag	Coverage Δ
unittests	86.23% <100.00%> (ø)

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[henrydingliu]

please pull main

[henrydingliu]

still seeing reversions on newer commits from main