show_key kitten: In kitty mode show the actual bytes sent by the terminal rather than a re-encoding of the parsed key event

Also port the kitten to Go

tools/cmd/tool/main.go

@@ -11,6 +11,7 @@ import (
 	"kitty/kittens/hints"
 	"kitty/kittens/hyperlinked_grep"
 	"kitty/kittens/icat"
+	"kitty/kittens/show_key"
 	"kitty/kittens/ssh"
 	"kitty/kittens/themes"
 	"kitty/kittens/unicode_input"
@@ -41,6 +42,8 @@ func KittyToolEntryPoints(root *cli.Command) {
 	ssh.EntryPoint(root)
 	// unicode_input
 	unicode_input.EntryPoint(root)
+	// show_key
+	show_key.EntryPoint(root)
 	// hyperlinked_grep
 	hyperlinked_grep.EntryPoint(root)
 	// ask

tools/tui/loop/key-encoding.go

@@ -105,6 +105,9 @@ type KeyEvent struct {
 	AlternateKey string
 	Text         string
 	Handled      bool
+
+	// The CSI string this key event was decoded from. Empty if not decoded from CSI.
+	CSI string
 }
 
 func (self *KeyEvent) String() string {
@@ -133,6 +136,7 @@ func KeyEventFromCSI(csi string) *KeyEvent {
 	if len(csi) == 0 {
 		return nil
 	}
+	orig_csi := csi
 	last_char := csi[len(csi)-1:]
 	if !strings.Contains("u~ABCDEHFPQRS", last_char) || (last_char == "~" && (csi == "200~" || csi == "201~")) {
 		return nil
@@ -165,7 +169,7 @@ func KeyEventFromCSI(csi string) *KeyEvent {
 	if len(sections) > 2 {
 		third_section = get_sub_sections(sections[2], 0)
 	}
-	var ans = KeyEvent{Type: PRESS}
+	var ans = KeyEvent{Type: PRESS, CSI: orig_csi}
 	var keynum int
 	if val, ok := letter_trailer_to_csi_number_map[last_char]; ok {
 		keynum = val