Per mara's review on #2881: the dropdown box chrome (background/border/
radius/shadow/min-width/white-space) and the trigger button's base
icon-button treatment are both reachable from hive-menu.css now --
the box chrome lives on hive-menu's own shadow-owned .menu-dropdown
wrapper (no slotting constraint at all), and the trigger button is
styled via ::slotted([slot='trigger']) since it's the top-level slotted
node for that slot. Item-row styling stays in the caller's stylesheet
-- ::slotted() only reaches directly-slotted elements, not their
descendants, so individual dropdown items are architecturally
unreachable from hive-menu's shadow tree. Verified interactively via
headless Chromium/CDP: trigger opacity/hover/border-radius and the
dropdown wrapper's background/border all resolve correctly, hover and
click-to-open still work.
8ebefeb0d5