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

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

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

@@ -1368,6 +1368,19 @@ export const dict: Record<I18nKey, string> = {
   "chat.statusRow.tasksTitle": "Tareas",
   "chat.statusRow.summary.activeLeft": "{active} activas · {left} restantes",
   "chat.statusRow.aborted": "Interrumpido",
+  "chat.revertIndicator.redo": "Rehacer",
+  "chat.revertIndicator.redoAria": "Rehacer — restaurar mensajes revertidos",
+  "chat.revertPopover.title": "Revertidos",
+  "chat.revertPopover.noTextContent": "Sin contenido de texto",
+  "chat.revertPopover.forkFromHere": "Bifurcar desde aquí",
+  "chat.revertPopover.forkFromMessage": "Bifurcar desde este mensaje",
+  "chat.revertPopover.restoreAll": "Restaurar todo",
+  "chat.revertPopover.restore": "Restaurar",
+  "chat.revertPopover.revert": "Revertir",
+  "chat.revertPopover.fork": "Bifurcar",
+  "chat.revert.toast.undo": "Revertido a {preview}",
+  "chat.revert.toast.redo": "Rehecho",
+  "chat.revert.toast.restored": "Todos los mensajes restaurados",
   "chat.errorBoundary.title": "Error en la conversación",
   "chat.errorBoundary.description": "La interfaz de la conversación encontró un error. Esto podría deberse a un problema de red temporal o a datos de mensaje corruptos.",
   "chat.errorBoundary.sessionLabel": "Sesión",