ux: remove duplicate smiley-face button on the emoji picker

The "Add emoji" formatting option rendered two clickable elements
stacked: the "Click to add emoji" text input AND a separate button
beside it with a smiley-face dashicon. Both opened the same dropdown
picker — visually duplicated and slightly confusing for users who
expected one or the other to be the trigger.

The button is gone. Clicking the input itself still opens the
picker (the existing JS already wired both .emoji-picker-button and
.emoji-input to the same click handler — the click handler now just
targets .emoji-input). Keyboard navigation (Enter/Space to toggle,
Escape to close) refocuses the input instead of the removed button.

Orphaned .emoji-picker-button CSS rule deleted.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -7,6 +7,17 @@ Format: [Keep a Changelog 1.1.0](https://keepachangelog.com/en/1.1.0/) — versi
 
 ## [Unreleased]
 
+### Changed — Removed duplicate smiley-face button on the emoji picker
+The "Add emoji" formatting option rendered two clickable elements
+stacked: the *"Click to add emoji"* text input AND a separate button
+beside it with a smiley-face dashicon. Both opened the same dropdown
+picker — visually duplicated and slightly confusing. The standalone
+button has been removed; clicking the input itself still opens the
+picker (the JS already wired both targets to the same handler).
+Keyboard navigation (Enter/Space to toggle, Escape to close)
+follows focus to the input instead of the now-gone button.
+Orphaned `.emoji-picker-button` CSS rule deleted.
+
 ### Changed — Menu labels: "Create WP Note" → "My Notes", "About WP Notes" → "About"
 - **"Create WP Note" submenu renamed to "My Notes"** (both in the WP
   Notes parent menu and the Tools → quick-access shortcut). The page