feat: switch text to UTF-8; add Unicode key events, dead keys & Czech layout; fix numpad navigation; add NumLock support

programs/src/dialogs/messagebox.cpp

@@ -143,7 +143,8 @@ void fit_text_end(const char* src, char* out, int out_len, int max_px) {
             gui::dialogs::safe_copy(out, out_len, candidate);
             return;
         }
-        keep--;
+        // Drop one whole character from the front of the tail
+        keep = slen - montauk::utf8::next_boundary(src, slen, slen - keep);
     }
 
     gui::dialogs::safe_copy(out, out_len, "...");