Integrate upstream through 31a677fe and retain both sides of the progress
trackers. Document the import tile, preview regression tests and helpers
to address CodeRabbit's docstring coverage warning.
The slider behavior and native acceptance evidence are unchanged. The PR
contains no published user-guide edits. Human contributor: tylerphotos.
Validation: cargo xtask ci on the integrated tree before committing.
Co-Authored-By: Codex <noreply@openai.com>