23d9f7c898
FileSessionStorage.#replaceSessionFileAfterEpermSync now unlinks the staged temp file when commitGuard returns false in both fallback branches: the ENOENT-vanished-target path and the post-move-aside path (where the moved-aside backup is also restored). Honors the writeTextAtomic contract that a guard-rejected stage is discarded. Regressions cover all three guard-reject exits: the direct rename pre-check, the ENOENT branch inside the EPERM fallback, and the move-aside branch that also restores the backup. Each asserts no orphan .tmp remains in the session dir. Fixes #4338