Chore: SlashCommands Preview (#28065)

...teor/app/lib/server/methods/executeSlashCommandPreview.ts

.../meteor/app/lib/server/methods/getSlashCommandPreviews.ts

apps/meteor/app/theme/client/imports/general/base_old.css

apps/meteor/app/theme/client/imports/general/theme_old.css

apps/meteor/app/ui-message/client/popup/ComposerBoxPopup.tsx

...nents/composerBoxPopup/ComposerBoxPopupCannedResponse.tsx

...pup/components/composerBoxPopup/ComposerBoxPopupEmoji.tsx

...opup/components/composerBoxPopup/ComposerBoxPopupRoom.tsx

...ponents/composerBoxPopup/ComposerBoxPopupSlashCommand.tsx

...opup/components/composerBoxPopup/ComposerBoxPopupUser.tsx

...nents/composerBoxPopupPreview/ComposerBoxPopupPreview.tsx

.../app/ui-message/client/popup/hooks/useComposerBoxPopup.ts

...-message/client/popup/hooks/useComposerBoxPopupQueries.ts

apps/meteor/client/components/ScrollableContentWrapper.tsx

...s/room/components/body/composer/messageBox/MessageBox.tsx

.../body/composer/messageBox/hooks/useMessageBoxAutoFocus.ts

...meteor/client/views/room/contexts/ComposerPopupContext.ts

...eor/client/views/room/providers/ComposerPopupProvider.tsx