feat: add parameterGroup options to share variables between peaks

[jobo322]

Refactor: introduce OptimizationLayout and parameterGroups

Summary:
This PR extracts optimizer-to-peak parameter mapping into a dedicated layout builder and adds linked parameters through parameterGroups. Multiple peak parameters can now share one optimization variable with optional factor and offset, without changing the optimizer itself.

Key changes:

• Added buildOptimizationLayout to centralize optimizer variable mapping.
• Added reconstructPeaks to centralize peak reconstruction.
• Wired optimize() and the fixed-parameter path to use the new layout/reconstruction helpers.
• Added OptimizeOptions.parameterGroups plus ParameterGroup and ParameterGroupMember.
• Added validation for invalid groups: unknown peak ids, duplicate members, incompatible flags/bounds, invalid factors, and non-finite offsets.
• For grouped variables, gradientDifference is computed conservatively as min(member.gradientDifference / |factor|).

Compatibility:

• Default behavior is unchanged when parameterGroups is not provided.
• Existing LM/direct optimization flows, the no-free-parameters path, and peak id preservation are preserved.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.76%. Comparing base (2b13c16) to head (353a899).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #126      +/-   ##
==========================================
+ Coverage   96.52%   97.76%   +1.24%     
==========================================
  Files           9       11       +2     
  Lines         230      358     +128     
  Branches       39       70      +31     
==========================================
+ Hits          222      350     +128     
  Misses          8        8              

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[lpatiny]

Need to try to optimiize a doublet superimposing a triplet like in