Polish snapshot_download_gh()

[hadley]

• Clarify meaning of dest_dir.
• Only emit hint in R-CMD-check jobs.

Fixes #2300

[claude]

Claude finished @hadley's task —— View job

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Code Review

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Review Summary

I've reviewed the changes in this PR which polish snapshot_download_gh(). The changes are minimal and focused on two specific improvements:

1. Documentation clarification: The dest_dir parameter documentation was updated from "Defaults to the current directory" to "Package root directory. Defaults to the current directory" - this clarifies the expected structure.

2. Conditional hint emission: The snapshot hint is now only emitted when GITHUB_JOB == "R-CMD-check" (line 126 in R/reporter-check.R), which prevents noise in other CI jobs.

Both changes are sensible improvements with no apparent bugs or issues. The test coverage validates the new conditional behavior.

LGTM