fix: streamline Heatmap feature logs

[phoman14]

Changes

• Report found transcripts and proteins before missing requested features.
• Keep missing-feature reports as informational messages without duplicate warning blocks.
• Add regression coverage for message order and absence of duplicate warnings.
• Add a NEWS entry for the user-facing log change.

Issues

None.

PR Checklist

• This comment contains a description of changes with justifications, with any relevant issues linked.
• Write unit tests for any new features, bug fixes, or other code changes.
• Update the docs if there are any API changes (roxygen2 comments, vignettes, readme, etc.). No API documentation change is needed.
• Update NEWS.md with a short description of any user-facing changes and reference the PR number.
• Run devtools::check() locally and fix all notes, warnings, and errors. Not run per requested focused-test scope; devtools::load_all() followed by tests/testthat/test-Heatmap.R passed locally (49 passes, 7 expected CRAN skips).