CVE-2026-54548: kas Persistently Disables SSH Host Key Checking

kas persistently disables SSH host key checking for the invoking user when internal SSH key setup is triggered via SSH_PRIVATE_KEY or SSH_PRIVATE_KEY_FILE and no user-specific SSH configuration file exists so far.

When this path is used, kas creates ~/.ssh/config with a global Host * rule containing StrictHostKeyChecking no. This was intended to ease the use of kas in short-lived CI environments that lack a pre-configured set of known hosts. In case a local user had no SSH configuration file so far, this approach weakens SSH host authenticity verification beyond the lifetime and scope of the kas command, increasing the risk of successful man-in-the-middle attacks against future SSH connections made by the same user.