Fix mode chip width on narrow cards

[thomasgregg]

Summary

• make the selectable mode chip the flex-row item instead of wrapping it in a differently sized box
• use an intermediate stacked layout for four-chip rows at phone widths so labels and values remain readable
• constrain both text tracks so long values and translations truncate inside their chip instead of crossing its border
• preserve dropdown positioning and stop backdrop clicks from bubbling back to the chip
• add regression coverage and rebuild the installable bundle

Verification

• npm test: 483 passing
• production-bundle suite: 483 passing
• browser sweep at every integer card width from 280–600 px: equal chip widths and no text outside any chip
• 394 px reproduction of the reported layout: Battery, Pressure, Mode/Intense+, and Head · time/0.5 h all remain fully visible

Closes #21