Prepare for CRAN submission

[jasdumas]

Problem

counselor is GitHub-only. CRAN publication would dramatically increase visibility and make installation trivial for the R community.

Tasks

• Pass R CMD check --as-cran with 0 errors, 0 warnings, 0 notes
• Ensure all examples use \dontrun{} or \donttest{} appropriately
• Add cran-comments.md with submission notes
• Verify all Suggests dependencies are properly conditioned
• Handle Python dependency gracefully (informative error if not configured)
• Ensure reticulate usage follows CRAN best practices
• Add inst/WORDLIST for spelling checks
• Test on R-devel, R-release, R-oldrel
• Test on Windows, macOS, Linux via GitHub Actions R-CMD-check

CRAN-Specific Considerations

• The reticulate dependency needs careful handling — CRAN checks run without Python
• Voice I/O functions must degrade gracefully when audio hardware unavailable
• System prompt files in inst/prompts/ should be documented
• API key requirements must be clearly noted (no CRAN check should try to call APIs)

Acceptance Criteria

• Clean R CMD check --as-cran on all 3 major platforms
• Submitted and accepted on CRAN