register_update_checker() guards on is_file + class_exists so the plugin
degrades cleanly on installs that ship without the vendored lib (no update
notices, but plugin core remains functional).
Settings::register_classifier_filters() registers priority-5 callbacks on
cf7stg_classifier_thresholds and cf7stg_hard_drop_rules so the UI options
actually influence Classifier behaviour. Called from Plugin::boot(). User
filters at priority 10 override these defaults as expected. Adds 4 tests
covering the wired behaviour and override priority. Also adds dry_run_drop?
to MessageFormatter::build() @param docblock.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Vladimir Bryzgalov