## Why
Windows non-TTY exec sessions reported interrupts as unsupported, so sending
Ctrl-C through `write_stdin` did not stop the running process.
## What changed
- Route interrupt requests for Windows non-TTY processes through their existing
termination callback, including pipe-backed processes.
- Track whether driver-backed Windows sessions use a TTY so PTY interrupts keep
their existing behavior.
- Consume the terminator after a successful interrupt to avoid invoking it again
when the process handle is dropped.
## Testing
Added coverage for local and remote exec-server sessions, unified exec, pipe
fallbacks, and legacy Windows sandbox processes.
GitOrigin-RevId: 34504d01f091ef57bb961e98ad5a8d9f1acee4ee