fix(worktrees): protect user changes across ambiguous move failures

Post-merge hardening of the session-to-worktree move (#2998), driven by
review findings on the follow-up pass:

- an ambiguous transport failure (relay abort, timeout) on the
  change-carrying move no longer force-deletes the fresh worktree that
  may hold the user's only copy of their changes; both intent kinds
  surface honest guidance and refresh both directories
- assertSdkSuccess re-tags ambiguous transport errors when wrapping SDK
  failures, so ambiguity classification survives the wrapper on every
  path, matching the prompt-send precedent
- session liveness checks scan all child stores plus the global status
  index, and report unknown (not idle) when no store covers the session
  — an evicted background directory can no longer make a busy session
  look movable
- incomplete-rollback errors carry the changes-may-be-in-destination
  guidance instead of swallowing it
- move-message assembly shared across the three call sites; tests now
  exercise the real ambiguity classifier (extracted to
  send-failure-classification.ts) instead of a hand-mirrored mock
- i18n fallout from the merge train: Turkish gains the 21 worktree-move
  keys, all 12 locales get the hedged ambiguous-failure toast; owning
  DOCUMENTATION.md files record the new contracts

packages/ui/src/components/layout/Header.tsx

@@ -71,7 +71,7 @@ import { copyTextToClipboard } from '@/lib/clipboard';
 import { buildExportFilename, downloadAsMarkdown, formatSessionAsMarkdown, saveAsMarkdownDesktop } from '@/lib/exportSession';
 import { Dialog, DialogContent, DialogDescription, DialogFooter, DialogHeader, DialogTitle } from '@/components/ui/dialog';
 import { Button } from '@/components/ui/button';
-import { requestSessionTreeMove, useIsSessionWorktreeMovePending } from '@/lib/worktrees/sessionWorktreeMove';
+import { buildSessionTreeMoveMessages, requestSessionTreeMove, useIsSessionWorktreeMovePending } from '@/lib/worktrees/sessionWorktreeMove';
 
 const DESKTOP_HEADER_ICON_BUTTON_CLASS = 'app-region-no-drag inline-flex h-8 w-8 items-center justify-center gap-2 rounded-md typography-ui-label font-medium text-foreground focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-primary disabled:pointer-events-none disabled:opacity-50 hover:bg-interactive-hover transition-colors';
 
@@ -1064,12 +1064,10 @@ export const Header: React.FC = () => {
       root,
       descendants,
       sourceDirectory: sessionDirectory,
-      messages: {
-        success: t('sessions.sidebar.session.moveToWorktree.success'),
-        failure: t('sessions.sidebar.session.moveToWorktree.failed'),
-        sourceVerificationFailed: t('sessions.sidebar.session.moveToWorktree.sourceVerificationFailed'),
-        applyChangesFailed: t('sessions.sidebar.session.moveToWorktree.applyChangesFailed'),
-      },
+      messages: buildSessionTreeMoveMessages(t, {
+        success: 'sessions.sidebar.session.moveToWorktree.success',
+        failure: 'sessions.sidebar.session.moveToWorktree.failed',
+      }),
     });
   }, [currentSessionId, isCurrentSessionActive, isCurrentSessionMovingToWorktree, sessionDirectory, t]);