Fix terminal instantly quitting by clamping initial POSIX terminal pty dimensions

[kangarko]

Fixes #313694
Relates to #313693

This clamps the initial pty dimensions passed to node pty on non Windows platforms.

TerminalProcess.resize() already clamps cols and rows to at least 1, but the initial spawn options still receive the constructor values directly. In the macOS arm64 Insiders regression, the terminal process can become ready, immediately hit a resize path with ioctl(2) failed, EBADF, and exit before the shell starts.

This keeps Windows startup behavior unchanged, including the existing Git Bash delayed resize path, and only normalizes the POSIX spawn options.

Validation I ran locally on the affected Insiders install:

• Integrated terminal starts and stays open
• stty size and tty return valid output
• nested zsh launches
• nonzero command exit does not kill the terminal
• interactive Python REPL accepts input through the pty
• output polling and terminal cleanup paths work
• large Unicode output plus stderr worked

I also made a separate user side workaround script for people stuck on the broken Insiders build, but that is intentionally not part of this PR.

[vs-code-engineering]

📬 CODENOTIFY

The following users are being notified based on files changed in this PR:

@anthonykim1

Matched files:

• src/vs/platform/terminal/node/terminalProcess.ts

[Copilot]

Pull request overview

Clamps the initial PTY dimensions passed to node-pty on non-Windows platforms to avoid spawning a PTY with invalid cols/rows (eg 0x0) which can trigger early ioctl(2) failed, EBADF failures and cause the integrated terminal to exit immediately (notably on macOS arm64 Insiders).

Changes:

• Clamp initial cols and rows to at least 1 for POSIX PTY spawn options.
• Preserve Windows behavior (including the existing Git Bash delayed-resize path that relies on 0x0).