Clean up rendered documentation output

[t-kalinowski]

Summary

• Remove the redundant printed label from the README confusion-matrix example.
• Hide the bare NULL result from the model-persistence save example.
• Regenerate the tracked pkgdown, LLM, and search artifacts.

Root cause

The README uses collapsed chunk output, so the cat() result appeared before the source expression that produced the matrix. The model-persistence save call also exposed its otherwise uninformative NULL result during rendering.

Impact

The public documentation renders each result beside the expression that produced it and omits an unhelpful serialization result. There are no public API or internal runtime changes.

Validation

• Rendered README.Rmd with rmarkdown.
• Rebuilt the pkgdown home page and model-persistence article, including LLM and search exports.
• Ran documentation output assertions and git diff --check.