## Why
Pipe spawning installs Unix `pre_exec` hooks, forcing a fork on macOS even though the shared child launcher supports native spawning.
## What changed
- Use the shared `Command` for pipe processes, enabling native macOS spawning while preserving session isolation, explicit descriptor inheritance, and Linux parent-death handling.
- Select `ReapOnly` so the pipe adapter retains ownership of process-tree termination.
- Track embedded NUL bytes in original Unix command inputs and reject them before spawning, including when invalid `current_dir` or `arg0` values are later replaced.
## Testing
Add macOS integration coverage verifying fork avoidance, executable path lookup, pipe I/O, session isolation, and descriptor inheritance. Add Unix regression tests for pipe and PTY fallback under descriptor pressure and for rejecting NUL inputs without running the child.
GitOrigin-RevId: f4fa2c1d3c1aee2c4ffa1dc2ff946f9f0b08eb20
## 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
## Why
Terminating a Windows execution session must also stop child processes, while a
normal root-process exit must continue to allow background descendants to run.
## What changed
- Assign Windows pipe, ConPTY, and sandbox processes to job objects and terminate
the job when a session is cancelled, times out, or is explicitly stopped.
- Preserve descendants when the root process exits normally.
- Attach ConPTY and sandbox processes to their jobs atomically at creation; keep
root-process termination as a fallback where job setup is unavailable.
## Testing
Added Windows coverage for descendant termination and preservation across pipe,
ConPTY, capture, cancellation, and legacy sandbox execution paths.
GitOrigin-RevId: 8f831f2fc4caaa7b79ce842a3ed7192bd02dd3b4
Charlie Marsh