remove SIGUSR1 escape; pkill <editor> is the standard recovery

The SIGUSR1 -> editor_emergency_kill wiring was a contrived escape
hatch. A console user with a stuck editor reaches for kill / pkill /
SIGKILL on the editor, not undocumented signals on the chat client.
editor_emergency_kill() stays for the internal Ctrl-Z abort path.

src/command/cmd_defs.c

@@ -2638,7 +2638,8 @@ static const struct cmd_t command_defs[] = {
       CMD_DESC(
               "Spawn external editor to edit message. "
               "After editing the inputline may appear empty. Press enter to send the text anyways. "
-              "Use /executable to set your favourite editor." )
+              "Use /executable to set your favourite editor. "
+              "Ctrl-Z in the editor aborts the session and returns to Profanity." )
     },
 
     { CMD_PREAMBLE("/correct-editor",

src/profanity.c

@@ -20,7 +20,6 @@
 #include <string.h>
 
 #include <glib.h>
-#include <glib-unix.h>
 
 #include "profanity.h"
 #include "common.h"
@@ -219,15 +218,6 @@ sigterm_handler(int sig)
     force_quit = TRUE;
 }
 
-// SIGUSR1 escape for an alive-but-stuck editor (WUNTRACED can't catch it).
-// Dispatched in the main loop. Trigger: `pkill -USR1 profanity`.
-static gboolean
-_emergency_resume_handler(gpointer data)
-{
-    editor_emergency_kill();
-    return G_SOURCE_CONTINUE;
-}
-
 static void
 sigtstp_handler(int sig)
 {
@@ -252,7 +242,6 @@ _init(char* log_level, char* config_file, char* log_file, char* theme_name)
     signal(SIGWINCH, ui_sigwinch_handler);
     signal(SIGTERM, sigterm_handler);
     signal(SIGHUP, sigterm_handler);
-    g_unix_signal_add(SIGUSR1, _emergency_resume_handler, NULL);
     if (pthread_mutex_init(&lock, NULL) != 0) {
         log_error("Mutex init failed");
         exit(1);