refactor(term): move conpty out of windows (#43)

* refactor(term): move conpty out of windows

To match golang/sys, the windows package should contain Windows specific
API calls. The conpty package is a high-level package that creates and
manages ConPty sessions, and thus wouldn't make sense to keep it under
windows.

* Update exp/term/conpty/conpty_other.go

exp/term/conpty/conpty_other.go

@@ -0,0 +1,14 @@
+//go:build !windows
+// +build !windows
+
+package conpty
+
+// ConPty represents a Windows Console Pseudo-terminal.
+// https://learn.microsoft.com/en-us/windows/console/creating-a-pseudoconsole-session#preparing-the-communication-channels
+type ConPty struct{}
+
+// New creates a new ConPty.
+// This function is not supported on non-Windows platforms.
+func New(int, int, int) (*ConPty, error) {
+	return nil, ErrUnsupported
+}

exp/term/windows/conpty/doc.go → exp/term/conpty/doc.go

@@ -3,3 +3,8 @@
 // https://learn.microsoft.com/en-us/windows/console/creating-a-pseudoconsole-session
 
 package conpty
+
+import "errors"
+
+// ErrUnsupported is returned when the current platform is not supported.
+var ErrUnsupported = errors.New("conpty: unsupported platform")