Fix lint findings in the R chunks of r-config.qmd #1429

lint-changed-files lints all of a changed file, and chapters/r-config.qmd carries 11 lint findings in its R chunks: commented code, lines over 80 characters, hanging indents, a single-quoted name, and = assignments.
Any PR that touches the file fails the check until they are fixed, which blocks #1428.

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https://claude.ai/code/session_01FWgYrDiMYAnjPMHWVTPJfZ