Add search and skin tones to profile emoji picker - #4910

Signed-off-by: kenny lopez <klopez4212@gmail.com>

The new picker assertions read overridden properties (48px control heights,
the resting search background) immediately after the search input becomes
visible. The Buzz stylesheet is appended from a `requestAnimationFrame` loop
that only starts once `em-emoji-picker` has attached its shadow root, so it
can land a frame or more later. An instrumented probe caught that gap: on 2
of 5 runs the shadow root had no `#buzz-emoji-mart-style` at that read point
and the input measured Emoji Mart's un-overridden 36px instead of 48px.

The shipped tests passed only because incidental round-trips bought enough
time. `expect(...).toBe(48)` does not retry, so the race was live.

Add `expectEmojiMartStylesInstalled` to the CSS helpers, polling for the
style element, and gate both specs on it before their un-retried reads. The
install loop itself predates this branch and is unchanged.

Also documents the second probe finding, which needed no fix: the resting
background samples as transparent right after install because Emoji Mart puts
a 225ms `background-color` transition on the input. It settles to
`rgb(229, 229, 230)`, and the override does win the cascade over the vendor
`var(--em-color-border)` rule.

Co-authored-by: kenny lopez <klopez4212@gmail.com>
Signed-off-by: kenny lopez <klopez4212@gmail.com>