macOS Chinese pinyin IME: pressing Enter to confirm a candidate word in
the group-chat composer submitted the draft as a message mid-composition.
The GroupMentionInput onKeyDown checked only `event.key === 'Enter' &&
!event.shiftKey` with no IME guard, unlike the core composer which guards
isComposing + keyCode 229 (#44135).
Add the same guard to the three Enter handlers in the bots plugin:
- GroupMentionInput (group composer + reply box) — the reported bug
- GroupClarifyCard free-text answer input — same premature-submit
- skill-hub search input — same premature-trigger
Closes#93528
quexiaolong