Force a UTF-8 ctype, stable buffer ids, redraw after deferred opens

- main: when the environment's locale is not UTF-8 (LANG unset, C/POSIX),
  switch LC_CTYPE to a UTF-8 locale so ncurses delivers and draws
  multibyte characters instead of dropping them.
- Buffer::Id(): a process-unique id that survives moves and is fresh for
  copies. The terminal renderer's skip and cursor caches and the reload
  confirmation now key on it rather than the buffer's address, which is
  reused after a buffer is closed.
- The reload confirmation is cancelled by any other command, like the
  quit confirmation.
- TerminalFrontend redraws when a deferred open starts a prompt or sets a
  status (e.g. the swap recovery question), not only when a buffer opens.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015rcVQiiWyTzoNrsvLSaAfB

TerminalFrontend.cc

@@ -1,4 +1,6 @@
 #include <cstdio>
+#include <ctime>
+#include <string>
 #include <ncurses.h>
 #include <termios.h>
 #include <unistd.h>
@@ -106,8 +108,18 @@ TerminalFrontend::Step(Editor &ed, bool &running)
 	ed.SetDimensions(static_cast<std::size_t>(r), static_cast<std::size_t>(c));
 
 	// Allow deferred opens (including swap recovery prompts) to run.
-	if (ed.ProcessPendingOpens())
-		changed = true;
+	// Its return value only reports an opened buffer; a deferred open that
+	// starts a prompt or sets a status must be drawn too.
+	{
+		const bool prompt_before = ed.PromptActive();
+		const std::string status_before = ed.Status();
+		const std::time_t status_time_before = ed.StatusTime();
+		if (ed.ProcessPendingOpens())
+			changed = true;
+		if (ed.PromptActive() != prompt_before || ed.Status() != status_before ||
+		    ed.StatusTime() != status_time_before)
+			changed = true;
+	}
 
 	// Handle all pending input before drawing: one key per frame made a
 	// pasted block take a frame (and a full redraw) per character. The first