fix: Add Windows compatibility and JupyterKernelClient fallback

[Yash-Kavaiya]

Fixes #100

Summary of Fixes

This PR adds native cross-platform support for Windows and resolves a runtime AttributeError:

1. Windows Console Compatibility (colab_cli/console.py):

   • Wrapped termios and tty imports in a try/except ImportError block.
   • Added guards around termios, tty, fileno(), and signal.SIGWINCH calls to prevent ModuleNotFoundError: No module named 'termios' on Windows.

2. Google Drive Auth /dev/tty Fallback (colab_cli/commands/automation.py):

   • Added a fallback for open("/dev/tty") on non-POSIX systems to use sys.stdin.readline().

3. JupyterKernelClient Fallback (colab_cli/runtime.py):

   • Fixed AttributeError: module 'jupyter_kernel_client' has no attribute 'KernelClient' in ColabRuntime.kernel_client by updating the fallback class name to jupyter_kernel_client.JupyterKernelClient.

Testing Verification

Verified end-to-end on Windows 11 with PowerShell:

• Created sessions using colab new --gpu T4 -s demo-session
• Handled OAuth flow & Drive automation
• Executed Python code & GPU workloads (nvidia-smi on Tesla T4 runtime)

[ramgeart]

Great work on adding Windows support to the CLI!

While testing this branch on Windows 11 with colab ssh --proxy-mode (e.g. for VS Code Remote - SSH and OpenSSH), we identified an issue where the proxy bridge terminates immediately after the server's SSH identification banner, causing OpenSSH to fail:

debug1: SSH2_MSG_KEXINIT sent
Connection closed by UNKNOWN port 65535
SSH server closed unexpectedly. Error code: 255

Root Cause in src/colab_cli/commands/ssh.py

1. select.select() fails on non-socket file descriptors on Windows:
   In _bridge_proxy_mode(), stdin_to_ws() calls:

   ready, _, _ = select.select([stdin_fd], [], [], None)

   On Windows, Python's select.select() only supports Winsock network sockets (not anonymous pipes, console handles, or file descriptors). Calling it on stdin_fd raises:
   OSError: [WinError 10038] An operation was attempted on something that is not a socket.
   The try...except (OSError, ...) catches this error and immediately runs _close_quietly(ws) in finally, killing the WebSocket connection right after the initial banner.
   Fix: Since stdin_to_ws runs in a dedicated daemon thread, we can bypass select.select on Windows and let os.read(stdin_fd, 8192) block natively.

2. Windows stdio mode & binary packet corruption:
   On Windows, sys.stdin and sys.stdout open in text mode by default. Binary SSH traffic is corrupted by automatic CRLF translation (\n <-> \r\n), and byte 0x1A (Ctrl+Z) is treated as EOF by the C runtime.
   Fix: Call msvcrt.setmode(sys.stdin.fileno(), os.O_BINARY) and msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY) when sys.platform == "win32".

3. Missing signal.SIGHUP on Windows:
   signal.SIGHUP does not exist in Python on Windows. Accessing it in _install_rm_signal_handlers() raises AttributeError whenever --rm is used.
   Fix: Guard signal.SIGHUP with hasattr(signal, "SIGHUP").

---

Suggested Patch

diff --git a/src/colab_cli/commands/ssh.py b/src/colab_cli/commands/ssh.py
index 1d5c4b6..e58b334 100644
--- a/src/colab_cli/commands/ssh.py
+++ b/src/colab_cli/commands/ssh.py
@@ -352,14 +352,20 @@ def _bridge_proxy_mode(ws: websocket.WebSocket) -> int:
     Returns:
       0 when either side closes.
     """
+    if sys.platform == 'win32':
+        import msvcrt
+        msvcrt.setmode(sys.stdin.fileno(), os.O_BINARY)
+        msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)
+
     stdin_fd = sys.stdin.buffer.fileno()
 
     def stdin_to_ws():
         try:
             while True:
-                ready, _, _ = select.select([stdin_fd], [], [], None)
-                if not ready:
-                    continue
+                if sys.platform != 'win32':
+                    ready, _, _ = select.select([stdin_fd], [], [], None)
+                    if not ready:
+                        continue
                 data = os.read(stdin_fd, 8192)
                 if not data:
                     break
@@ -528,7 +534,10 @@ def _install_rm_signal_handlers(do_rm: Callable[[], None]) -> None:
         do_rm()
         os._exit(0)
 
-    for sig in (signal.SIGHUP, signal.SIGTERM, signal.SIGINT):
+    signals = [signal.SIGTERM, signal.SIGINT]
+    if hasattr(signal, 'SIGHUP'):
+        signals.append(signal.SIGHUP)
+    for sig in signals:
         try:
             signal.signal(sig, _on_signal)
         except (ValueError, OSError):

All 50 unit tests in tests/test_ssh.py pass with this change.

---

How to Connect on Windows (VS Code / OpenSSH)

With this fix applied, connecting from Windows works smoothly:

1. Configure ~/.ssh/config (C:\Users\<username>\.ssh\config):

   Host colab
       HostName colab
       User root
       IdentityFile C:\Users\<username>\.ssh\id_ed25519
       IdentitiesOnly yes
       ProxyCommand colab ssh --proxy-mode -s colab
       StrictHostKeyChecking no
       UserKnownHostsFile NUL
       ServerAliveInterval 30
       ServerAliveCountMax 4
   

   (Note: Passing -s <session_name> like -s colab is recommended because colab ssh will automatically provision a new runtime session if none exists, routing output to stderr so the SSH byte stream remains clean).

2. Connect:

   • Terminal:

     ssh colab

   • VS Code / Cursor Remote - SSH:
     Press Ctrl+Shift+P -> Remote-SSH: Connect to Host... -> Select colab.