fix(editor): follow live terminal size in external editor

The compose editor is spawned via fork+execvp and inherits profanity's
LINES/COLUMNS, which hold the size captured at startup and are never
refreshed on resize. A curses editor (nano, vim, ...) honors them over
the real window, so it renders at the launch-time size after a resize.

Drop LINES/COLUMNS from the child's environment before forking so its
curses falls back to ioctl(TIOCGWINSZ). Assembling the env in the parent
lets the child only reassign environ instead of calling unsetenv()
between fork and exec, keeping it clear of unsetenv()'s allocator work in
the multithreaded fork->exec window. profanity itself is unaffected.

src/tools/editor.c

@@ -25,6 +25,8 @@
 #include "ui/ui.h"
 #include "xmpp/xmpp.h"
 
+extern char** environ;
+
 typedef struct EditorContext
 {
     gchar* filename;
@@ -140,6 +142,22 @@ launch_editor(gchar* initial_content, void (*callback)(gchar* content, void* dat
     GSource* sigchld_warmup = g_child_watch_source_new(getpid());
     g_source_unref(sigchld_warmup);
 
+    // Build the editor's env without LINES/COLUMNS pre-fork, so the child only
+    // reassigns environ instead of calling unsetenv() between fork and exec.
+    // The editor's (n)curses then reads the live window via ioctl(TIOCGWINSZ).
+    gsize env_len = 0;
+    while (environ[env_len]) {
+        env_len++;
+    }
+    gchar** editor_env = g_new0(gchar*, env_len + 1);
+    gsize env_kept = 0;
+    for (gsize i = 0; i < env_len; i++) {
+        if (g_str_has_prefix(environ[i], "LINES=") || g_str_has_prefix(environ[i], "COLUMNS=")) {
+            continue;
+        }
+        editor_env[env_kept++] = environ[i];
+    }
+
     pid_t pid = fork();
     if (pid == -1) {
         log_error("[Editor] Failed to fork: %s", strerror(errno));
@@ -148,12 +166,15 @@ launch_editor(gchar* initial_content, void (*callback)(gchar* content, void* dat
         ui_resize();
         cons_show_error("Failed to start editor: %s", strerror(errno));
         g_strfreev(editor_argv);
+        g_free(editor_env); // array only; strings are borrowed from environ
         g_free(ctx->filename);
         g_free(ctx);
         return TRUE;
     } else if (pid == 0) {
         // Child process: Inherits TTY from parent
 
+        environ = editor_env; // live TIOCGWINSZ size, not the inherited LINES/COLUMNS
+
         // SIGTSTP=SIG_DFL lets vim's :stop / Ctrl-Z work; profanity catches
         // the STOPPED state via editor_check_stopped() and drops to the shell.
         signal(SIGINT, SIG_DFL);
@@ -170,6 +191,7 @@ launch_editor(gchar* initial_content, void (*callback)(gchar* content, void* dat
     editor_pid = pid;
     g_child_watch_add((GPid)pid, _editor_exit_cb, ctx);
     g_strfreev(editor_argv);
+    g_free(editor_env); // frees the parent's array only; the child keeps its own COW copy until execvp
     return FALSE;
 }