fix(tabs): remove close hover fill

[helbertm]

Summary

• preserve the 26px close/rename hit targets
• remove hover and focus background fills from inline tab actions
• color only the close X with the danger color on hover
• keep the external keyboard focus ring

Validation

• npm run validate:full:ci
• npm run validate:browser:quality
• npm run validate:native:chromium
• Da Vinci release checkpoint: approved with no blocking findings