feat(ui): revert indicator with undo/redo, message list, and attachment restore (#1279)

* feat(ui): revert indicator with undo/redo, message list, and attachment restore

Add bidirectional undo/redo with redo stack navigation and expandable
revert indicator in StatusRow. List reverted messages with inline
revert/fork actions. Restore file attachments on revert.

- Add revert indicator with count, expandable popover, per-button spinner
- Restore file/image attachments when reverting to a message
- Clear previous attachments on revert when target has none
- Restore-all bypasses redo stack for direct unrevert
- Survive popover close/reopen without losing loading state
- Fix flash when sending message after revert
- Fix count disappearing on browser refresh
- Remove dead code (undoStack, getRevertHistory, fork-from-here)
- Fix toast grammar (Undid -> Reverted, Redid -> Redone)
- Add i18n keys for revert popover across all locales

* fix(ui): Greptile review fixes and i18n for revert toasts

- Fix handleSlashUndo toast always showing [No text] (moved getSyncParts before revertToMessage)
- Add inputStore rollback in revertToMessage catch (restore attachments + text on API failure)
- Change portal ID to per-session (prevent multi-session collisions)
- Add i18n keys for undo/redo/restored toasts across all 7 locales
- Use formatMessage in store for localized toast strings

* fix(ui): add missing sessionId to click-outside effect deps

* fix(ui): remove unused sessionActions import in ChatMessage

* fix(ui): derive revert dock from session state

---------

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/lib/i18n/messages/ko.ts

@@ -1404,6 +1404,19 @@ export const dict: Record<I18nKey, string> = {
   'chat.statusRow.tasksTitle': '작업',
   'chat.statusRow.summary.activeLeft': '{active}개 활성 · {left}개 남음',
   'chat.statusRow.aborted': '중단됨',
+  'chat.revertIndicator.redo': '다시 실행',
+  'chat.revertIndicator.redoAria': '다시 실행 — 되돌린 메시지 복원',
+  'chat.revertPopover.title': '되돌림',
+  'chat.revertPopover.noTextContent': '텍스트 없음',
+  'chat.revertPopover.forkFromHere': '여기서 분기',
+  'chat.revertPopover.forkFromMessage': '이 메시지에서 분기',
+  'chat.revertPopover.restoreAll': '모두 복원',
+  'chat.revertPopover.restore': '복원',
+  'chat.revertPopover.revert': '되돌리기',
+  'chat.revertPopover.fork': '분기',
+  'chat.revert.toast.undo': '{preview}(으)로 되돌림',
+  'chat.revert.toast.redo': '다시 실행',
+  'chat.revert.toast.restored': '모든 메시지 복원됨',
   'chat.errorBoundary.title': '채팅 오류',
   'chat.errorBoundary.description': '채팅 인터페이스에서 오류가 발생했습니다. 일시적인 네트워크 이슈 또는 손상된 메시지 데이터 때문일 수 있습니다.',
   'chat.errorBoundary.sessionLabel': '세션',