Terminal reporting not working: 'not a tty'

### Description `tty` and `ps` commands fail to detect terminal when run under gVisor. This is easiest to show with Docker, but if `runsc` is run directly with the `"terminal": true` in the config, it has the same problem. ``` $ docker run --runtime=runsc -it --rm ubuntu tty not a tty ``` ``` $ docker run --runtime=runsc -it --rm ubuntu ps t PID TTY STAT TIME COMMAND 1 ? Rs 0:00 ps t ``` Compare to the output with the default Docker runtime: ``` $ docker run -it --rm ubuntu tty /dev/pts/0 ``` ``` $ docker run -it --rm ubuntu ps t PID TTY STAT TIME COMMAND 1 pts/0 Rs+ 0:00 ps t ``` ### Steps to reproduce _No response_ ### runsc version ```shell runsc version release-20260608.0 spec: 1.2.1 ``` ### docker version (if using docker) ```shell ``` ### uname _No response_ ### kubectl (if using Kubernetes) ```shell ``` ### repo state (if built from source) _No response_ ### runsc debug logs (if available) ```shell ```