Scoped to the two stated fixes only: strips the #composerModelDropdown position:fixed
mobile override that #6104's branch had bundled in (that's the #6080 model-picker
mechanism, being reworked separately to reparent to body level — the fixed override
is trapped by .composer-footer's container-type so it doesn't belong here), and drops
the <=360px tool-name-hiding rules (header overflow-clip prevents the spill without
losing tool identity). Thanks @webtecnica.