feat: Linux packaging, SDK v0.7.1, fix rawmode conflict

- go.mod: SDK pseudo-version -> v0.7.1 (remote tag), go.sum updated
- cmd/waiter/rawmode_linux.go: remove (conflicts with raw_unix.go)
- cmd/gui/package.json: add rpm/AppImage Linux targets
- package/package-linux.sh: cross-distro packaging script (deb/tar.gz/rpm)
- package/linux/: DEBIAN control files, postinst/prerm, RPM spec

cmd/waiter/rawmode_linux.go

@@ -1,25 +0,0 @@
-//go:build linux
-
-package main
-
-import (
-	"syscall"
-	"unsafe"
-)
-
-func setRawMode(fd int) (func(), error) {
-	var old termios
-	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), TCGETS, uintptr(unsafe.Pointer(&old))); err != 0 {
-		return func() {}, err
-	}
-	new := old
-	new.Lflag &^= ICANON | ECHO | ISIG
-	new.Cc[VMIN] = 1
-	new.Cc[VTIME] = 0
-	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), TCSETS, uintptr(unsafe.Pointer(&new))); err != 0 {
-		return func() {}, err
-	}
-	return func() {
-		syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), TCSETS, uintptr(unsafe.Pointer(&old)))
-	}, nil
-}