Simplify ofeanalysis to a barebones R package scaffold

[Copilot]

Summary

• Reduced the repository to a minimal, coherent R package baseline so future modules can be added intentionally without carrying placeholder scaffolding.
• Package surface
  • Kept only validate_ofe_data() as the exported API.
  • Removed placeholder/unused module files (cleaning, models-basic, plots, reporting, summary-means, utils).
  • Removed related tests for deleted functionality.
• Package metadata/docs
  • Trimmed DESCRIPTION dependencies to only what is needed now (testthat in Suggests).
  • Updated NAMESPACE to export only validate_ofe_data.
  • Updated README.md and NEWS.md to reflect the simplified current scope.

library(ofeanalysis)
validate_ofe_data(data.frame(plot = 1:3, response = c(2.1, 2.5, 2.3)))

Testing

• Existing validation tests for validate_ofe_data() remain in place.
• Local R test/build execution was not possible in this environment (R/Rscript unavailable).
• PR-level parallel validation completed with no review comments and no CodeQL issues.