fix(editor): avoid Ctrl-Z hang on the editor child, add SIGUSR1 escape

The upstream signal reset in launch_editor set SIGTSTP back to SIG_DFL in
the child, letting Ctrl-Z (or vim's :stop) stop the editor. GLib's
g_child_watch uses waitpid(WNOHANG) without WUNTRACED, so a STOPPED
editor never wakes the watch and the app freezes until killed externally.
Other TUI chat clients carry this open problem for years (see
weechat/weechat#985, open since 2017); shells solve it with full job
control (setpgid + tcsetpgrp + WUNTRACED), which is heavy for our use
case.

Drop just the SIGTSTP reset. SIGINT and SIGPIPE are still set to SIG_DFL
— Neovim's libuv needs SIGINT-as-default to recognise an interactive
terminal (per upstream commit dd76f9087). SIGTSTP stays inherited as
SIG_IGN from profanity's _init, so Ctrl-Z and vim's :stop become no-ops
inside /editor. Losing vim's :stop during message composition is an
acceptable trade for not freezing the whole app.

As a universal escape hatch for any other "hung editor" scenario
(looping $EDITOR, corrupted tty, anything we cannot detect), install a
SIGUSR1 handler via g_unix_signal_add that sends SIGTERM to the editor
child via editor_emergency_kill(). The existing g_child_watch then
dispatches the normal exit callback, ui_resume runs, and the user is
back in profanity. Recovery from another terminal: `pkill -USR1
profanity`.

src/profanity.c

@@ -20,6 +20,7 @@
 #include <string.h>
 
 #include <glib.h>
+#include <glib-unix.h>
 
 #include "profanity.h"
 #include "common.h"
@@ -182,6 +183,16 @@ sigterm_handler(int sig)
     force_quit = TRUE;
 }
 
+// Universal "I'm stuck in the editor" escape hatch. Dispatched in the main
+// loop by GLib (g_unix_signal_add), so it is safe to call into editor.c
+// directly. Trigger from another terminal: `pkill -USR1 profanity`.
+static gboolean
+_emergency_resume_handler(gpointer data)
+{
+    editor_emergency_kill();
+    return G_SOURCE_CONTINUE;
+}
+
 static void
 _init(char* log_level, char* config_file, char* log_file, char* theme_name)
 {
@@ -193,6 +204,7 @@ _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);

src/tools/editor.c

@@ -40,11 +40,13 @@ typedef struct EditorContext
 // editor that fights the first one for the terminal, then prematurely
 // ui_resume when either exits.
 static gboolean editor_active = FALSE;
+static pid_t editor_pid = 0;
 
 static void
 _editor_exit_cb(GPid pid, gint status, gpointer data)
 {
     editor_active = FALSE;
+    editor_pid = 0;
 
     EditorContext* ctx = data;
     gchar* contents = NULL;
@@ -157,9 +159,11 @@ launch_editor(gchar* initial_content, void (*callback)(gchar* content, void* dat
     } else if (pid == 0) {
         // Child process: Inherits TTY from parent
 
-        // Reset signal handlers that profanity sets so the editor doesn't inherit them
+        // SIGTSTP intentionally NOT reset: keeping SIG_IGN inherited via
+        // fork+exec avoids hanging on a STOPPED editor (g_child_watch lacks
+        // WUNTRACED). Cost: vim's :stop is a no-op in /editor. See
+        // editor_emergency_kill for other hung-editor scenarios.
         signal(SIGINT, SIG_DFL);
-        signal(SIGTSTP, SIG_DFL);
         signal(SIGPIPE, SIG_DFL);
 
         if (editor_argv && editor_argv[0]) {
@@ -169,7 +173,20 @@ launch_editor(gchar* initial_content, void (*callback)(gchar* content, void* dat
     }
 
     // Parent process: Watch the child asynchronously
+    editor_pid = pid;
     g_child_watch_add((GPid)pid, _editor_exit_cb, ctx);
     g_strfreev(editor_argv);
     return FALSE;
 }
+
+void
+editor_emergency_kill(void)
+{
+    if (!editor_active || editor_pid <= 0) {
+        return;
+    }
+    log_warning("[Editor] emergency resume: sending SIGTERM to editor pid %d", editor_pid);
+    kill(editor_pid, SIGTERM);
+    // g_child_watch dispatches _editor_exit_cb when the child exits, which
+    // already restores the UI — no further action required here.
+}

src/tools/editor.h

@@ -16,4 +16,9 @@
 
 gboolean launch_editor(gchar* initial_content, void (*callback)(gchar* content, void* data), void* user_data);
 
+// Universal escape hatch: if an editor session is active, send SIGTERM to the
+// child. The existing g_child_watch fires _editor_exit_cb on exit, which
+// already restores the UI. Wired to SIGUSR1 in profanity.c.
+void editor_emergency_kill(void);
+
 #endif