feat(editor): add asynchronous external editor support

The synchronous `get_message_from_editor` blocked the main loop (`prof_run`) while launching an external editor like `vim`, halting network I/O in `session_process_events` and preventing incoming message reception.

Introduced `get_message_from_editor_async` for `cmd_editor` to run the editor asynchronously. It forks and execs the editor in a thread (`editor_thread`), suspending NCurses to free the terminal. The main loop skips `inp_readline` and `ui_update` via a new `background_mode` flag while the editor runs, allowing `session_process_events` to keep the connection alive.

On editor completion, `editor_process` (called per loop iteration) resumes NCurses with `ui_resize`, inserts the result into the readline buffer and clears `background_mode`.

Retained synchronous `get_message_from_editor` for ~20 existing code paths (e.g., `vcard_nickname`) to avoid breaking them.

Tested with `vim` and `nano`: confirms no rendering conflicts, messages received during editing, and seamless resume. Edge cases like editor crashes handled via error logging and seamless resume.

src/profanity.c

@@ -59,6 +59,7 @@
 #include "config/tlscerts.h"
 #include "config/scripts.h"
 #include "command/cmd_defs.h"
+#include "tools/editor.h"
 #include "plugins/plugins.h"
 #include "event/client_events.h"
 #include "ui/ui.h"
@@ -93,6 +94,9 @@ static void _connect_default(const char* const account);
 pthread_mutex_t lock;
 static gboolean force_quit = FALSE;
 
+// main.c (prof_run section)
+gboolean background_mode = FALSE;
+
 void
 prof_run(gchar* log_level, gchar* account_name, gchar* config_file, gchar* log_file, gchar* theme_name, gchar** commands)
 {
@@ -118,42 +122,44 @@ prof_run(gchar* log_level, gchar* account_name, gchar* config_file, gchar* log_f
         log_stderr_handler();
         session_check_autoaway();
 
-        line = commands ? *commands : inp_readline();
-        if (commands && line && memcmp(line, "/sleep", 6) == 0) {
-            if (!g_timer_is_active(waittimer)) {
-                gchar* err_msg;
-                if (strtoi_range(line + 7, &waittime, 0, 300, &err_msg)) {
-                    g_timer_start(waittimer);
-                    /* Increase the minimal runtime by the waiting time
-                     * so we can be sure there's runtime left after executing
-                     * the last command.
-                     */
-                    min_runtime += waittime;
-                } else {
-                    log_error(err_msg);
-                    g_free(err_msg);
-                    commands = NULL;
+        if (!background_mode) {
+            line = commands ? *commands : inp_readline();
+            if (commands && line && memcmp(line, "/sleep", 6) == 0) {
+                if (!g_timer_is_active(waittimer)) {
+                    gchar* err_msg;
+                    if (strtoi_range(line + 7, &waittime, 0, 300, &err_msg)) {
+                        g_timer_start(waittimer);
+                        /* Increase the minimal runtime by the waiting time
+                         * so we can be sure there's runtime left after executing
+                         * the last command.
+                         */
+                        min_runtime += waittime;
+                    } else {
+                        log_error(err_msg);
+                        g_free(err_msg);
+                        commands = NULL;
+                    }
+                } else if (g_timer_elapsed(waittimer, NULL) >= waittime) {
+                    g_timer_stop(waittimer);
+                    commands++;
+                    if (!(*commands))
+                        commands = NULL;
+                }
+                cont = TRUE;
+            } else if (line) {
+                ProfWin* window = wins_get_current();
+                cont = cmd_process_input(window, line);
+                if (commands) {
+                    commands++;
+                    if (!(*commands))
+                        commands = NULL;
+                } else {
+                    free(line);
+                    line = NULL;
                 }
-            } else if (g_timer_elapsed(waittimer, NULL) >= waittime) {
-                g_timer_stop(waittimer);
-                commands++;
-                if (!(*commands))
-                    commands = NULL;
-            }
-            cont = TRUE;
-        } else if (line) {
-            ProfWin* window = wins_get_current();
-            cont = cmd_process_input(window, line);
-            if (commands) {
-                commands++;
-                if (!(*commands))
-                    commands = NULL;
             } else {
-                free(line);
-                line = NULL;
+                cont = TRUE;
             }
-        } else {
-            cont = TRUE;
         }
 
 #ifdef HAVE_LIBOTR
@@ -163,7 +169,12 @@ prof_run(gchar* log_level, gchar* account_name, gchar* config_file, gchar* log_f
         notify_remind();
         session_process_events();
         iq_autoping_check();
-        ui_update();
+
+        editor_process(wins_get_current());
+
+        if (!background_mode) {
+            ui_update();
+        }
 #ifdef HAVE_GTK
         tray_update();
 #endif