fix: initialize pseudo console with default size for SSH sessions (#20472)

Resolved an invalid parameter error (-2147024809) during PTY creation on
Windows 11 22H2 (but not only) when connecting via JetBrains Toolbox
which spawns the native SSH client with `-tt` forcing PTY allocation
even though there is no "terminal" on the client side to query its size.

CreatePseudoConsole doesn't accept a 0x0 (zero width and zero height)
console size and unfortunately, there is NO explicit documentation in
the official Microsoft documentation that states the minimum valid
values or explicitly prohibits 0x0.

Looking at real-world implementations in the search results, all
examples use reasonable non-zero values.

I tested this with a local Windows VM registered to dev.coder.com i.e.
externally managed workspace.

Fixes: #20468

pty/pty_windows.go

@@ -54,10 +54,19 @@ func newPty(opt ...Option) (*ptyWindows, error) {
 		return nil, err
 	}
 
-	consoleSize := uintptr(80) + (uintptr(80) << 16)
+	// Default dimensions
+	width, height := 80, 80
 	if opts.sshReq != nil {
-		consoleSize = uintptr(opts.sshReq.Window.Width) + (uintptr(opts.sshReq.Window.Height) << 16)
+		if w := opts.sshReq.Window.Width; w > 0 && w <= 65535 {
+			width = w
+		}
+		if h := opts.sshReq.Window.Height; h > 0 && h <= 65535 {
+			height = h
+		}
 	}
+
+	consoleSize := uintptr(width) + (uintptr(height) << 16)
+
 	ret, _, err := procCreatePseudoConsole.Call(
 		consoleSize,
 		uintptr(pty.inputRead.Fd()),