Add independent Remote input helper with EOF and watchdog cleanup

cmd/cthulhu-input-helper/main.go

@@ -0,0 +1,56 @@
+// Copyright (c) 2026 Storm Dragon
+// Authors: Storm Dragon, Angus Kola
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package main
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"git.stormux.org/storm/cthulhu/internal/platform/xorg"
+	"git.stormux.org/storm/cthulhu/internal/remoteinput"
+)
+
+func main() {
+	if err := run(); err != nil && !errors.Is(err, context.Canceled) {
+		// No key names, epoch, native diagnostics or argument/parser excerpts.
+		fmt.Fprintln(os.Stderr, "Remote input helper failed")
+		os.Exit(1)
+	}
+}
+
+func run() error {
+	flags := flag.NewFlagSet("cthulhu-input-helper", flag.ContinueOnError)
+	flags.SetOutput(io.Discard)
+	epoch := flags.Uint64("epoch", 0, "private input epoch")
+	if flags.Parse(os.Args[1:]) != nil || flags.NArg() != 0 || *epoch == 0 {
+		return remoteinput.ErrProtocol
+	}
+	control, err := remoteinput.AdoptPipe(os.Stdin, false)
+	if err != nil {
+		return err
+	}
+	defer control.Close()
+	output, err := remoteinput.AdoptPipe(os.Stdout, true)
+	if err != nil {
+		return err
+	}
+	defer output.Close()
+	// Descriptor 3 is a separate, empty lifetime pipe. Its EOF must not wait
+	// behind control frames buffered before owner death or cancellation.
+	lifetime, err := remoteinput.AdoptPipe(os.NewFile(3, "remote-input-lifetime"), false)
+	if err != nil {
+		return err
+	}
+	defer lifetime.Close()
+	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer stop()
+	return xorg.ServeRemoteKeyHelper(ctx, *epoch, control, lifetime, output)
+}