Fix recent-emoji list leaking into UI on unrelated parent rebuild

[Fintasys]

Problem

Reported in #238: selecting an emoji while the RECENT tab is visible could make the recent list suddenly re-order/jump later, in reaction to an unrelated rebuild triggered by a parent widget.

Root cause

EmojiPickerState.updateRecentEmoji(refresh: false) only gated the setState() call with the refresh flag — it always mutated _categoryEmoji regardless:

_recentEmoji = recentEmoji;
_categoryEmoji[recentTabIndex] = _categoryEmoji[recentTabIndex].copyWith(
  emoji: _recentEmoji.map((e) => e.emoji).toList(),
);
if (mounted && refresh) {
  setState(() {});
}

_categoryEmoji is the same list instance held by reference in EmojiViewState (_state = EmojiViewState(_categoryEmoji, ...)), and DefaultEmojiPickerView rebuilds the recent grid straight from it on every build(). So on the RECENT tab, tapping an emoji reorders the data silently (no setState, no visible change) — but the next stray rebuild from a parent widget paints that already-mutated data, and the recent list jumps.

This is exactly the inconsistency described in the #238 discussion: "it updates the list in the state, but doesn't update the UI".

Fix

Skip the displayed-category mutation entirely when refresh is false. The persisted store is already updated by the caller (addEmojiToRecentlyUsed / addEmojiToPopularUsed write before this call), so nothing is lost — the change simply becomes visible on the next explicit refresh instead of leaking in early.

Test

Adds test/recent_emoji_state_test.dart:

• refresh:false must not leak — persists a recent emoji via the public EmojiPickerUtils.addEmojiToRecentlyUsed API (which calls updateRecentEmoji(refresh: false)), then forces an unrelated parent rebuild and asserts the recent tab is unchanged. Fails on the old code, passes with the fix.
• refresh:true updates immediately — asserts an explicit refresh still renders the new recent emoji right away.

Full suite (15 tests) passes; flutter analyze clean.

🤖 Generated with Claude Code