The legacy Fomantic `line-height: 1` on buttons made ellipsized button
text clip descenders like `g` letters, like in the PR target branch
selector. Selection dropdowns were 3px taller than the inputs and
buttons next to them because their padding assumed `line-height: 1em`.
- Buttons and selection dropdowns use `--line-height-default` with
smaller vertical padding, `min-height` keeps their sizes for every font
including CJK
- Remove overrides that only compensated for the old values and dropdown
declarations that never applied
- Label-edit and push-mirror modals use regular-size action buttons like
all other modals