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/session/sidebar/DOCUMENTATION.md

@@ -20,6 +20,12 @@ kept at this root in `types.ts` and `utils.tsx`.
   changes and roll back session-only if a later descendant fails. The root moves
   last and carries source changes once, which prevents rollback from replaying the
   transferred patch into the source.
+- Failure cleanup: a worktree created for the move is removed only after a
+  definite failure. When the change-carrying request fails without confirming
+  its outcome, that worktree is KEPT (it may hold the only copy of the user's
+  changes), both directories are refreshed authoritatively because the session
+  may have moved server-side, and the toast points the user at the destination.
+  Existing destinations are never removed; they get the same guidance.
 
 `MainLayout` and `VSCodeLayout` call `useSessionListSync({ isVSCode })`
 unconditionally. The hook publishes complete directory bootstrap demand,