- Add dropdown_popup_width helper in common.rs replacing magic formula heuristics
- Implement is_wide range table to count East Asian Wide/Fullwidth (CJK) glyphs double for localized strings
- Calibrate unit scale factor to 0.68 * font_size preserving existing width behavior at font size 11
- Apply shared calculation across viewport controls and ribbon dropdowns
- Update unit tests to verify width calculation on standard and CJK labels