Normalize download message filename display

Summary

Normalize user-visible download lifecycle and part-file status messages so file name arguments use the bracketed display form.

Acceptance Criteria

• [x] New-download logs and notifications show [ file name ].
• [x] Duplicate download warnings show [ file name ].
• [x] Recovered part.met and user-visible part-file load/save errors show bracketed file names for the download name argument.
• [x] Download completion keeps the bracketed file name and no longer appends the legacy smiley to the English string.
• [x] Actual file names, persisted metadata, and list-column file names are not changed.

Implementation Notes

• This uses the existing FormatDisplayFileName() helper and relies on its idempotence to avoid double wrapping.
• Localized resource files were left untouched; code-side filename formatting applies regardless of the active language.