Standardize PPC messages to warn/inform

[utkarshpawade]

Fixes #461

Summary
This PR standardizes user-facing messaging by replacing base warning() and message() calls with rlang::warn() and rlang::inform() in selected PPC code paths.

Changes

• Replaced warning() with rlang::warn() in ppc_loo().
• Replaced message() with rlang::inform() in ppc_loo().
• Replaced message() with rlang::inform() in ppc_censoring().
• Replaced message() with rlang::inform() in ppc_test_statistics().

The message content and trigger logic remain unchanged.

Why
bayesplot already uses rlang conditions in several places. Using warn() and inform() ensures more consistent condition handling and better interoperability with rlang-based workflows.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.63%. Comparing base (e8234b4) to head (7fb682e).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #462      +/-   ##
==========================================
+ Coverage   98.55%   98.63%   +0.08%     
==========================================
  Files          35       35              
  Lines        5864     5863       -1     
==========================================
+ Hits         5779     5783       +4     
+ Misses         85       80       -5     

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[Copilot]

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[jgabry]

Thanks, looks good. We can merge if all the tests pass.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

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[jgabry]

Don't worry about the copilot suggestions, I don't think they're necessary

[utkarshpawade]

ohh thanks !

[jgabry]

Thanks!