croc: Overwrite-confirmation bypass via a crafted "croc-stdin-" filename on receive

croc is a tool that allows any two computers to simply and securely transfer files and folders. Prior to 11.5.2, the receive-side file-readiness loop in src/croc/croc.go treats any sender-controlled basename beginning with croc-stdin- as a trusted text-transfer artifact even when SendingText is false. This skips askReceiveOverwrite and rename handling for a predictable exact-name collision in the receiver's working directory, allowing a remote sender whose transfer the user accepts to overwrite or truncate a matching regular file through recipientInitializeFile, or to remove and replace a matching destination with an empty file or an in-directory symlink through createEmptyFileAndFinish, without confirmation. The impact is limited to pre-existing names in the croc-stdin- namespace that the sender can predict; other filenames retain the prompt, dotfiles outside that namespace are not reachable, and symlink targets remain confined to the receive directory. This issue is fixed in version 11.5.2.