refactor: Maintain single code path for package manager execution (#256)

* refactor: Maintain single code path for package manager execution

* fix: Avoid context leak during interactive TTY read

* fix: PTY flow handling

* fix: Linter fixes

internal/pty/input_read_unix.go

@@ -0,0 +1,57 @@
+//go:build !windows
+
+package pty
+
+import (
+	"context"
+	"errors"
+	"io"
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+func readInput(ctx context.Context, src io.Reader, buf []byte) (int, error) {
+	file, ok := src.(*os.File)
+	if !ok {
+		select {
+		case <-ctx.Done():
+			return 0, ctx.Err()
+		default:
+			return src.Read(buf)
+		}
+	}
+
+	fd := int32(file.Fd())
+	pollFds := []unix.PollFd{{Fd: fd, Events: unix.POLLIN}}
+
+	for {
+		select {
+		case <-ctx.Done():
+			return 0, ctx.Err()
+		default:
+		}
+
+		n, err := unix.Poll(pollFds, 100)
+		if err != nil {
+			if errors.Is(err, unix.EINTR) {
+				continue
+			}
+
+			return 0, err
+		}
+
+		if n == 0 {
+			continue
+		}
+
+		revents := pollFds[0].Revents
+		if revents&(unix.POLLERR|unix.POLLHUP|unix.POLLNVAL) != 0 {
+			return 0, io.EOF
+		}
+
+		if revents&unix.POLLIN != 0 {
+			return file.Read(buf)
+		}
+	}
+}